PROCEEDINGS

AMERICAN ACADEMY

ARTS AND SCIENCES.

NEW SERIES. Vol. VI.

WHOLE SERIES. Vol. XIV.

FROM MAY, 1878, TO MAY, 1879. SELECTED FROM THE RECORDS.

BOSTON: PRESS OF JOHN WILSON AND SON.

1879.

xd' d 3

CONTENTS.

PAGE

I. On the Young Stages of Bony Fishes. By Alexander

Agassiz 1

II. Experiments upon Piezometers used in Hydraulic Invesliga-

lions. By Hiram F. Mills, Civil Engineer ... 26

III. Researches on the Substituted Benzyl Compounds. Fourth

Paper. By C. Loring Jackson and Alfred W. Field 54

IV. The Development of Lepidosteus. By Alexander Agas-

siz 65

V. Researches in Telephony. By Professor Dolbear . . 77

VI. On Certain Remarkable Groups in the Lower Spectrum. By

Professor S. P. Langley 92

VII. On the Temperature of the Sun. By Professor S. P.

Langley 106

VIII. On the Heat Produced by the Rapid Magnetization and De- magnetization of the Magnetic Metals. By John Trow- bridge, S.D., and Walter N. Hill, S.B 114

IX. Methods of Measuring Electric Currents of Great Strength ; together with a Comparison of the Wilde, the Gramme, and the Siemens Machines. By John Trowbridge . 122

X. Descriptions of some New Species of North American Mosses.

By Leo Lesquereux and ThOmas P. James . . . 133

XI. Distributions of Heat in the Spectra of various sources of Ra- diation. By Wm. W. Jacques, Ph. D 142

XII, On the Limits of Accuracy in Measurements with the Micro- scope. By Professor Edward W. Morley . . . 164

IV CONTENTS.

PAGE

XIII. On the Limits of Accuracy in Measurements with the Tele-

scope and the Microscope. By Pkofessor William

A. Rogers 168

XIV. Preliminary Report on the Echini of the Exploring Ex-

pedition of H. M. S. " Challenger," Sir C. Wyville Thomson, Chief of Civilian Staff. By Alexander Agassiz 190

XV. Contributions to American Botany. By Sereno Watson.

1. Revision of the North American Liliaceaz 213

2. Descriptions of some New Species of North American

Plants 288

XVI. A Neiv Receiving Telephone. By Professor A. E. Dol-

bear 304

XVII. Researches on the Substituted Benzyl Compounds. Fifth

Paper. By C. Loring Jackson and J. Fleming White 306

Proceedings 321

Memoirs: —

Jacob Bigelow ( 332

Hon. Caleb Cushing, LL.D. .....' 342

Silas Durkee, M.D 343

John Barnard Swett Jackson . . ' . • .' 344

John Clarke Lee 352

John Mudge Merrick, S.B 353

Benjamin Franklin Thomas 354

William Cullen Bryant 355

Joseph Henry 356

Stephen Thayer Olney 367

George B. Wood 368

Friedrich Wilhelm Ritschl 369

Karl Freiherr Von Rokitanski 370

List of the Fellows and Foreign Honorary Members . . 373

Index ■ 381

PROCEEDINGS

OF THE

AMERICAN ACADEMY

OP

ARTS AND SCIENCES.

VOL. XIV. PAPERS READ BEFORE THE ACADEMY.

>

OLOGIGAL LABORATORY.

Received t h-. ^ . 7 A ". 7 d

Accession No. u H. \)

Given by *2lT .?' ,,<*~-^^ ><■< -'v.. /V1^ r*. '^

Place,

*^*Ho book op pamphlet is to be pemoved fpom the Uab- opatopy without the pepmission of the Trustees.

;, pre- bony sarlier mtion sents, 1 and e de- * the I. fig. o this again, beyond calling attention to the peculiar pnysiognomy oi these young bony fishes, while in the stages (PI. III. figs. 3-5, and PI. IV. fio-. 1) during which the heterocercal tail is so prominent a feature, and before the fins characteristic of the osseous fishes have become wholly or partially differentiated from the primitive embryonic fin-fold, which extends from the base of the head, and runs more or less parallel with the dorsal chord, round the anal extremity, back toward the anterior

* Proceedings Am. Acad. Arts and Sciences, xiii. 117. Boston, 1877. vol. xiv. (n. s. vi.) 1

■^BHBHaH^HHHHHHflHHHHBKl

IV CONTENTS.

PAGE

XIII. On the Limits of Accuracy in Measurements with the Tele-

scope and the Microscope. By Professor William

A. Rogers 168

XIV. Preliminary Report on the Echini of the Exploring Ex-

pedition of H. M. S. " Challenger," Sir C. Wyville Thomson, Chief of Civilian Staff. By Alexander Agassiz 190

XV. Contributions to American Botany. By Sereno Watson.

1. Revision of the North American Liliacece 213

2. Descriptions of some New Species of North American

Plants 288

XVI. A Neiv Receiving Telephone. By Professor A. E. Dol-

bear 304

XVII. Researches on the SuhiHUifaii /?/>.>■*•.<' ^ ' *""

Papt

Proceedings

Memoirs: — Jacob Bige] Hon. Caleb Silas Durke John Barna Johu Clarkt John Mudgt Benjamin F William Cu Joseph Hem Stephen Tru George B. W Friedrich W

Karl Freiherr Von Rokitanski

OUi)

370

List of the Fellows and Foreign Honorary Members . . 373 Index ■ 381

em>

PROCEEDINGS

OF THE

AMERICAN ACADEMY

OF

ARTS AND SCIENCES.

VOL. XIV. PAPERS READ BEFORE THE ACADEMY.

I.

ON THE YOUNG STAGES OF BONY FISHES. By Alexander Agassiz.

Presented May 28, 1878.

II. Development of the Flounders.

A young Flounder, immediately after its escape from the egg, pre- sents no special points of difference from the embryos of other bony fishes, in a similar stage of growth. There are, however, in the earlier stages also many points in common, to which but little attention has been paid, thus far ; and the study of these characters presents, from an embryological point of view, many features of special and also of more general interest. As I have already treated of the de- velopment of the tail and head (in Part I. of these Studies),* the gradual passage from a leptocardial tail, such as we find in PI. III. fig. 1, to a so-called homocercal tail (PI. IV. fig. 5), I will not refer to this again, beyond calling attention to the peculiar physiognomy of these young bony fishes, while in the stages (PI. HI. figs. 3—5, and PL IV. fig. 1) during which the heterocercal tail is so prominent a feature, and before the fins characteristic of the osseous fishes have become wholly or partially differentiated from the primitive embryonic fin-fold, which extends from the base of the head, and runs more or less parallel with the dorsal chord, round the anal extremity, back toward the anterior

* Proceedings Am. Acad. Arts and Sciences, xiii. 117. Boston, 1877. vol. xiv. (n. s. vi.) 1

Z PROCEEDINGS OF THE AMERICAN ACADEMY

part to the anal opening. Their general resemblance, at this time, to the Ganoid types of older periods, and especially to the Amias of the present day, cannot be too strongly insisted upon. In the Flounders, there is usually but a single dorsal and anal fin, formed from the original embryonic fin-fold. I will only notice, in a general way, the separation of the anal and dorsal from the caudal, by the earlier ap- pearance of the permanent fin-rays ; and the more rapid growth of the caudal, during the time when, in the dorsal and anal fin, the em- bryonic fin-rays, which disappear with the growth of the permanent ones, are still the most prominent feature. Little by little, however, with the increase in depth of dorsal and anal (PL IV. figs. 2, 3, 4, 5), the separation between these and the base of the caudal becomes more abruj3t ; and this, accompanied by the gradual shrinking of the rem- nant of the embryonic fin-fold at the base of the caudal both above and below, soon brings the relations of the three principal fins of the Flounders to the proportions they bear in the adult (PI. IV. fig. 5). In another species (PL IX.), I shall describe the gradual development of the anterior dorsal out of the primitive embryonic fin-fold. In the bony fishes, neither the development of the ventrals nor the pectorals has yet been traced from a lateral embryonic fin-fold ; but, in sharks and skates, the case is different. (See J. "Wyinan,* in his development of Raja.)

We may perhaps find hereafter, in the development of such forms as Lumpus, Liparis, and the like, a nearer approach to the Selachian mode of development of the paired fin-rays. In those of the bony fishes the development of which I have had an opportunity of following, the pectorals are well developed ; early assuming, even while in the egg, the Ganoid (Crossopterygian) type, to which I have already alluded in the first part of this paper.f In some of the earlier stages, the lat- eral embryonic fold, from which the pectorals are formed, can be dis- tinctly traced, — though never assuming the great prominence which it has in the dorsal or anal embryonic folds, the paired fins early con- cealing the lateral folds ; while it is the reverse with the dorsal and anal folds, from which the dorsal and anal fins are developed late.

The ventrals, on the contrary (PL VI. fig. 5, PL VII. fig. 4, PL IX. fig. 6), make their appearance very much later, and, in our Flounders, at

* "Wtmajt, Jeffries. Observations on the Development of Raja Batis, in Mem. Am. Acad. Boston, 1864. And also Balfour, F. M. Elasmobranch Fishes.

+ Agassiz, Alexander. On the Young Stages of Osseous Fishes. Proc. Am. Acad. xiii. Boston, 1877.

OF ARTS AND SCIENCES. 3

first as a mere swelling of the median line, behind the hyoid bone ; this (PL IV. figs. 3-5) grows quite rapidly ; the permanent fin-rays at once make their appearance, — the anterior ones (the outer) first ; and there is nothing special to note in the further development of the ven- trals, which soon resemble, on a small scale, the ventrals of the adult. The ventrals possess, at no time, embryonic fin-rays, like those of the dorsal, anal, and caudal fins, formed from the longitudinal embryonic fin-fold. In the pectorals, embryonic fin-rays also precede the forma- tion of the permanent rays ; but in many bony fishes (PI. VI. fig. 5, PI. X. fig. 1), these permanent rays appear very early, — before those of other paired or unpaired fins, — the Crossopterygian stage being passed while still in the egg. ■

A striking characteristic of the young of all bony fishes is the extraordinary development of the pigment cells (chromatophores and chromatoblasts), and the great changes they undergo during the growth of the embryo. Pouchet* has more recently called attention to the wide-spread existence of these pigment spots, so well known to all students of Invertebrates. He studied them especially among the Fishes, in connection with the atrophism of the color on the blind sides of Flounders ; pointing most plainly to the partial atrophy of the great sympathetic nerve, effected during the passage of the eye from the right to the left, or vice versa, as the cause. The power of the nervous system over the complicated system of pigment spots, which produces eventually the coloring of the adult fish, is of course much more readily traced in the younger stages, while the individual cells are still isolated, and before their anastomoses have become so com- plicated that it is well-nigh impossible, even in quite young specimens, to follow the changes resulting from any special nervous excitement. Conrpare, for instance, the simple chromatic system of cells of PI. II. figs. 1-4, with the more and more complex anastomosing branches of PL III. figs. 5 and PL IV. figs. 1-5. This is still better seen, perhaps, if we compare PL VI. figs. 1-3 (young Flounders, just hatched from the egg, and a couple of days old) with PL VI. figs. 5-7, showing the gradual passage of the few, large, well-individualized chromatic cells of PL VI. fig. 3, into the innumerable system of small cells, closely packed and crowded in spots, so as to form the special design charac- teristic of this species. f

* Pouchet, G. Des Changements de Coloration sous l'lnfluence des Nerfs. Archives de Physiologie et d'Anatomie. 1876.

t Pouchet has succeeded in producing a white side in trouts, by destroying the eye of that side. Rev. Scient. xiii. 1877.

4 PROCEEDINGS OF THE AMERICAN ACADEMY

The young Flounder has already attained a considerable size, before any signs appear of the change in the position of the eye on the left side (see PI. III. figs. 3-5 and PI. IV. fig. 1), and before the young fish shows the least tendency to favor one side over the other. Not until the young fish is fully three-eighths of an inch in length can the first slight difference be perceived in the position of the two eyes (when seen from above), the left eye being somewhat in advance of the other. In this species, the Flounder eventually lies down on the left side, which becomes colorless. In order to prevent repetitions, we shall call this the case of a right Flounder (dextral), — that is, of a Flounder colorless on the left side, and where the left eye has passed over to the right side, — calling the sides, at the same time, either blind or white, and the opposite ocular or colored.

Plates III. and IV. show very well the changes of form through which the young dextral Flounder passes before it finally assumes the appearance of the adult, and habitually rests with its colorless side upon the ground. All young Flounders, even long after they have all the characteristics of the adult, very frequently swim vertically for quite a length of time, or else swim near the surface, with the undulating movement they have when swimming over the bottom, their heads well raised, and bodies carried flat, parallel to the surface. Even quite old Flounders sometimes are caught swimming near the top of the water. Almost all the stages figured in Plates III. and IV. were caught near the surface, swimming vertically, like any other young bony fishes ; but this they do only when they come up to feed, while the water is very smooth, about ten in the morning, on very bright sunny days, when they may be seen eagerly devouring swarms of embryo Crustaceans, of all orders. The young of other fishes seem to share this habit ; for of the latter I have examined no less than twenty-five species, caught at va- rious times with a hand-net, swimming near the surface of the water, on bright sunny days, when not a ripple ruffled the sea. "With the least movement, all the more delicate of these embryos vanish ; leav- ing only the older and more vigorous, which in their turn disappear, and seek shelter in deeper water. Only when the young fishes are old enough to be recognized as the young of their tribes, do they ven- ture to join them in their ordinary haunts.

PI. V. figs. 7-11, PI. VI., and PI. VII., on the other hand, give us in general the changes of form a young sinistral Flounder undergoes from the time it leaves the egg until it assumes the characteristics of the adult. The explanation of the plate will give all the necessary details of the changes, which are mere repetitions of those described

OF ARTS AND SCIENCES. 5

in Pis. III. and IV. ; with the exception, of course, that the blind, colorless side is now found on the right side of the fish, the left side being the chromatic side. This species, as compared with the dex- tral species, is remarkable for the greater development of the pig- ment cells, figured on Pis. III. and IV. The young Flounder (PI. VI. fig. 7), when not more than three-fourths inches long, is already quite opaque, the whole colored side being thickly covered with minute pigment cells : they extend also upon the dorsal and anal, in irregular blotches, forming only in later stages the patterns which characterize some of the species among our Flounders. It is not uncommon for a peculiar pattern to appear quite early (see Pis. VII. and IX.).

In the present species, the pigments of the dorsal and anal do not appear before the stage figured on PI. VI. fig. 5.

As will be seen, on an examination of the figures of PI. VI., the earlier stages (Figs. 1-5) are readily recognized by the total absence of pigment cells in the extremity of the caudal. This feature still persists, in quite well-advanced individuals (PI. VI. figs. 6, 7, 8). The tail, in this species, passes rapidly through the heterocercal stages, and does not present the striking external resemblance to that of Ganoids, so characteristic of the species figured in Pis. III. and IV.

On PI. V., additional details have been given of the mode of trans- fer of the eye from the one side to the other, — either the right eye to the left side, or vice versa, — which, with the figures of the embryos, on Pis. III., IV., VI., will show very clearly how the transfer is accomplished, in the ordinary case of a dextral or sinistral Flounder.

While still in the egg (PI. V. fig. 6), and for some time after hatch- ing (PI. V. figs. 1, 2, 7, PI. III., PL IV. fig. 1, PI. VI. figs. 1-4), the eyes of the two sides are placed symmetrically on each side of the longitudinal axis. The first change — and the process is identical, whether we take a right or a left Flounder — is the slight advance towards the snout (PI. V. fig. 3) of the eye about to be transferred ; so that the transverse axis, passing through the pupil of the eyes, no longer makes a right angle with the longitudinal axis. This move- ment of translation is soon followed by a slight movement of rota- tion ; so that, when the young fish is seen in profile, the eyes of the two sides no longer appear in the same plane, — that on the blind side being now slightly above and in advance of that on the colored side (PI. IV. fig. 2, PI. V. fig. 5, PI. VI. fig. 5, PI. IX. fig. 7). With increasing age, the eye on the blind side rises higher and higher to- wards the median longitudinal line of the head ; a larger and larger part of this eye becoming visible from the colored side, where the

6 PROCEEDINGS OF THE AMERICAN ACADEMY

embryo is seen in profile (see PI. IV. figs. 3-5, PL VI. figs. 6, 7, PI. V. figs. 8-12, PI. VII. fig. 5), until the eye of the blind side has, for all practical purposes, passed over to the colored side (PI. V. figs. 4, 11).

The rapidity and extent of this translation and rotation of the eye from the blind to the colored side can be best seen on comparing the profiles of the heads (PI. V. figs. 5, 10) of a dextral and a sinistral Flounder with the profiles seen from the colored sides, before the eyes have begun their movement (PI. I., PI. VI. fig. 6, PI. VII. fig. 5).

As the dorsal, little by little, with advancing age, extends along the head towards the nostrils, it soon, in old specimens, finds its way behind the eye which has come from the blind side (compare the position of the anterior part of the dorsal, in PI. VI. figs. 5 and 7, in PI. IV. figs. 2 and 5, and PI. VIII. fig. 3). This continued advance of the dorsal anteriorly, after the eye has passed to the colored side, naturally gave rise to a great many theories respecting the passage of the eye through the head, under the anterior part of the dorsal fin ; and many natu- ralists, after an examination of the twisted facial part of the skull on the adult, have attempted most ingenious explanations of the mode by which the eye reached its ultimate position.

The facts contained in this paper leave no doubt that, at any rate, in the majority of the Flounders of our coast (I have traced the devel- opment of eight species), the transfer of the eye from the blind side to the color side occurs very early in life, while all the facial bones of the skull are still cartilaginous, and that long before their ossifica- tion the eye has been transferred, by a combined process of translation and rotation, to the colored side. Let x, y, z be rectangular axes ; and, if we call the longitudinal axis of the body twisting x, the trans- verse axis at the extremity of which the eyes are placed in the plane xy, the first change taking place is that x is no longer at right angles with y, though the eyes are still in plane xy. The next change is that the plane in which the eyes are now placed (x'y1) makes an angle with the xy ; cutting 2 at a slight distance above the origin of the co- ordinate axes, the eye of the colored side forming the apex of the angle. This angle gradually increases, until it passes beyond the plane yz, when the eye from the blind side has reached the colored side.

The subsequent modifications of the frontal bone, owing to the aberrant position of the eye from the colorless side, are interesting on account of their connection with abnormal anatomical features found in the Flounders ; but they explain in no wise the mode in which the transfer of the eyes has taken place, this being anterior to any essen- tial changes in the frontal bone. In early life, the strong muscles which

OF ARTS AND SCIENCES. 7

control the motion of the eyeball in the young Flounder maintain also a very powerful strain upon the frontal bone while still cartilaginous and readily flexible, and no doubt help to twist it in accordance with the gradual change in the position of the eyes.

While the observations of Malm on the young stages of Flounders tended to show the improbability of the eye passing through the skull from the blind side to the binocular, the observations of Steenstrup on the genus Plagusia, seemed, for that genus, at any rate, to show clearly that the eye did pass through the tissues of the head, during its transfer from the blind to the binocular side. But neither Malm nor Steenstrup, nor subsequently Schiodte, actually traced the changes undergone dur- ing the process. Steenstrup's specimens were alcoholic ; and, although his theory was substantiated by observations on a number of in- termediate stages of the passage of the eye through the tissue, yet, on the other hand, the observations of Malm, making it probable that the eye merely went round the head, in a manner not yet explained, were equally precise. I had myself traced quite a number of Flounders, in all of which the eye was transferred in accordance with the process described in the commencement of this paper, and figured on Pis. III.- VIII., — a process completely in accordance with the suppositions of Malm, and in direct contradiction to the theory of Steenstrup. In the late summer of 1875, however, I traced to my satisfaction the development of a very transparent Flounder (PI. X. fig. 1), — so transparent, indeed, as to rival the most watery of Jelly Fishes. When placed in a flat glass dish, it could only be distinguished by allowing the light to strike it in certain directions : otherwise, all that was visible were the two apparently disembodied bright emerald eyes, moving more or less actively.

In this Flounder (PI. X. fig. 1), already of a considerable size, — over an inch in length, — the position of the eyes was perfectly sym- metrical. They were placed also at considerable distance from the anterior extremity of the snout ; so that, judging from the size of the fish and the position of the eyes, as well as from the extension of the dorsal almost to the nostrils, I inferred that I had a new Flounder, in which the eyes would probably always remain more or less symmetri- cal, and in which the transfer of the eye from one side to the other was replaced by the exceeding transparency of the body, allowing either eye, owing to the great range of motion of the eyes both in a vertical and horizontal direction, — a feature characteristic of all Flounders, — to be really useful on both sides of the body. A Flounder can move his pupil vertically and horizontally through an

8 PROCEEDINGS OP THE AMERICAN ACADEMY

angle of at least one hundred and eighty degrees. Thus, our trans- parent Flounder, which I did not at first recognize as the Plagusia of Steenstrup, could readily, by looking obliquely, see with great distinct- ness, through the transparent tissues, what was passing on the opposite side of the body.

I made all prepai'ations to watch the changes in this interesting fish, should any such take place ; and, a couple of days afterwards, I noticed the first change in the position of the eye (PI. X. fig. 3) of the right side. No less than fifteen of these transparent Flounders were caught at the surface, with the hand-net, at the mouth of the harbor of Newport, close to the shore, on a very quiet and brilliant morning. They were then swimming vertically, and rushing violently after the minute Entomostraca swarming on the surface ; but, as soon as they were confined in shallow glass jars, they turned on the right side, where they would often remain immovable on the bottom for hours. They were rapid in their movements when disturbed ; frequently jumping out of the water and over the sides of the dishes, to a considerable distance. Though they appear so delicate, they do not seem to suffer, any more than other Flounders, from their momentary stay on dry land. When swimming vertically, they usually move obliquely, the tail kept much lower than the head ; and, when seen endways, are more or less curved, owing to the extreme tenuity of their body (PL X. fig. 2).

During the change of the eye from the blind to the binocular side of the body, the outline of the young fish becomes more rounded anteriorly ; and the minute, dotlike yellow and black pigment spots, hardly perceptible in Fig. 1, PI. X., form somewhat more prominent patches on the sides of the body, and radiating lines parallel to the fin-rays on the dorsal and anal fins (PI. X. fig. 11).

The right eye (PI. X. fig. 3) could, when the fish was in profile, be seen through the head slightly in advance, and somewhat above the left eye ; the right eye in that position, owing to the great transparency of the body, being quite as useful as if it had been placed on the left side. In the following stages, the right eye rises gradually more and more above the left eye, in a somewhat oblique direction towards the fifth or sixth anterior ray of the dorsal, until the fifth or sixth day, when the right eye can be seen entirely clear of the left eye, well above it (PI. X. fig. 4). Owing to the great size of the orbit, the left eye, when seen from the left side (PL X. fig. 3), sometimes appears shot a little behind the right, especially after the motion of rotation has commenced ; for we find that in this Flounder, as well as in the others, the transfer of the

OF ARTS AND SCIENCES. \)

eye from the right side to the left takes place by means of a movement of translation, accompanied and supplemented by a movement of rota- tion over the frontal bone. But, in this case, very special conditions attend the transfer, which, at first sight, seem to make the passage of the eyes of this species an exceptional one. I think we can easily show that the present mode of transfer does not differ so radically as would at first seem from the conditions described in the other species, in the beginning of this paper. When the right eye of the young Flounder has reached the frontal bone, and approaches the base of the dorsa1, we find, on turning the fish on his left side, that the right eye is no longer on the outer surface of the right side. It no longer occu- pies, as in the earliest stages, a huge orbit, capable of extensive move- ments in all directions ; but unlike the left eye, which has retained all its former powers of locomotion, as well as its original place, it has gradually sunk deep into the tissues of the base of the dorsal fin, between it and the frontal, — having sunk, indeed, to such an extent that the huge orbit, so characteristic of all Flounders, has gradually become reduced to a mere circular opening. Through this opening, the eye now communicates with the exterior ; while, from its posi- tion above the frontal (PI. X. fig. 4), it has, when the pupil turns to the opposite direction, a perfectly unobstructed vision through the transparent left side of the body. Little by little, the opening on the right becomes smaller and smaller ; and as, at the same time, the eye pushes its way deeper into the tissues, an additional opening is now formed on the left side (PL X. fig. 7), through which the right eye can now communicate directly with the left exterior on the left side of the body. Thus, in the stage intermediate between PI. X. fig. 4 and PI. X. fig. 8, we find no less than three orbital openings : one large one, — the original one of the left eye ; a smaller one, on the left side also, the new orbit formed for the right eye, as it has pushed its way through the tissues of the base of the dorsal fin ; and a small orbit on the right side, the remnant of the original right orbit of the right eye, which, before the right eye has completely passed over to the left side, becomes entirely closed (PI. X. fig. 8). With the continued sinking of the right eye, the gradual resorption of the tissues, and the closing up of the old orbit, as the eye works its way across the head, we eventually get the right eye entirely over to the left side. It has now, by a movement of translation and of rotation, penetrated through the tissues between the base of the dorsal fin and the frontal bone ; having apparently passed through the head, as was suggested to Steenstrup, by his examination of the alcoholic speci-

10 PROCEEDINGS OF THE AMERICAN ACADEMY

mens which furnished him the materials for his paper on Plagusia. The present transparent species evidently belonged to this genus (Pla- gusia) ; and I had thus succeeded in actually tracing, in one and the same individual, the passage of the right eye to the left side through the head.

If we now compare this method of transfer of the eye through the head with the transfer previously described round the frontal bone on the exterior of the head, we can readily see that the difference is not as great as it would appear at first sight. Were we to imagine this species of Plagusia with a dorsal, stopping in the anterior median line behind the posterior edge of the eyes, the transfer would then take place exactly as in the case of the common Flounders. The right eye would travel round the frontal, without having to sink into the tissues ; and, if subsequently to the transfer of the right eye to the binocular side, the anterior portion of the dorsal were to extend in advance of the anterior edge of the eyes to the intermaxillary, we should then obtain a result identical with that described before, and one which actually occurs in precisely this manner as we have seen in a number of Flounders ; and the mere resorption of the tissues at the base of the anterior part of the dorsal, while interesting as a short-cut to an end, is not of so great physiological value, or so im- portant as a difference in the method of the transfer of the eye, as appears on a first examination.

Owing to the transparency of this Plagusia, several interesting struc- tural details could readily be followed, which only tedious manipulation would have demonstrated in the other more opaque species, of which the development is here given. Among these were the great length of the optic nerve, which allows, as it were, sufficient slack to be taken in during the transfer of the eye from the right to the left side (PL X. figs. 4, 8, 9), so as apparently not to interfere in any way with the sight of the right eye ; also, the immense accumulation of muscular bands forming the sheath of the orbits of the eyes, and providing for the great variety and range in the movements of the eyeball and lids (PI. X. figs. 3, 4, 5, 8, 9) ; also the direct and very active circulation taking place to and from the heart with the cavity of the orbit of the eyes. (See PI. X. fig. 9, where the direction of the arrows shows the course of this current.) The presence of this circulation of a so- called ocular heart can be readily traced in the adult of our Halibut.

The Flounders have thus far only been found in the most recent geological deposits : they seem to belong peculiarly to the present period. It is certainly remarkable that no Flounders should have

OP ARTS AND SCIENCES. 11

been discovered among the true bony fishes, which date back as far as the Jurassic Period. To whatever cause we may ascribe the peculiar development of the Flounders, it seems to have been inactive during the periods immediately preceding our own ; and, in the absence of any plausible explanation of their appearance and development during the present period, we must look to some exceedingly subtle agency, of which we have at present no conception. The causes usually as- signed for the development of fishes with a binocular side are all unsatisfactory ; and all are invalidated by the fact that similar condi- tions constantly fail to produce like results. The Flounders are usually said, for instance, to rest on one side, because the great width of the body makes it the most natural position ; but there are many other fishes of far greater width which always swim vertically, and never show any tendency to assume the pleuronect mode of locomotion. In fact, the great development of the dorsal and ventral fins gives to Flounders special advantages over other fishes for maintaining a ver- tical position. The young Flounder also shows a tendency thus to rest on one side, at a time when the young fish is much like any other fish, long before the habit could be of any special benefit or use.

The absence of a swimming-bladder has also been assigned as a prin- cipal cause of the peculiar mode of locomotion among Flounders. But there is one of our Flounders in which a swimming-bladder is already well developed in the young fish ; and this does not prevent that particular species from adopting, as early as the others, the Flounder mode of locomotion.

The only other cause we can assign is that broad fishes, like the Flounders, find it of course much easier to pursue their prey, if, while swimming close to the bottom, they are protected from detec- tion by a complicated system of pigment cells, for producing col- ors or patterns within certain limits, so as to resemble sand, mud, or gravel. This would gradually lead to the exclusive use of one side (should the fish lie on either side), and would result in the atrophy of the eye, unless the fish were able to transfer his eye to the other side, and thus retain it ; when, as a secondary cause from this, the atrophy of the pigment cells of one side would follow. If this, however, is the natural explanation, why do not we find Flounders in almost all fami- lies of fishes, — at least, among the broad forms of the group, — and why were they not as common in earlier times as at the present day ? "We have also to face a very interesting point of heredity. It would certainly seem far simpler for the Flounders to hand down, from gen- eration to generation, the two eyes on one side of the body, and

12 PROCEEDINGS OF THE AMERICAN ACADEMY

further to hatch their young, as other fishes do, with the characters of the adult ; instead of leaving for a future period (and a period of great mortality among them) the development of the transfer of the eyes to the right or left, — thus transmitting merely the tendency, and not the thiug itself, as we find to be the case in Acalephs (Hybocodon), in the Tunicates, Salpae, in the Gasteropods, in the Polyzoa, &c. Yet this tendency is very well defined ; for we rarely meet with dextral forms when the Flounder is sinistral, or vice versa ; and I have, in our common Flounders, met with no instances of reversal in the course of the development. In Plagusia only did I notice such a reversal, where there was an attempt made in many cases — seven out of fif- teen cases — by the young fish to force the left eye to pass to the right side by lying down on the left, but in no case did this prove suc- cessful ; and, after a while, the young fish showed traces of brain dis- ease, and soon died, usually before the process of transfer of the eye had made much progress, — showing that a violation of the nor- mal mode of transfer cannot readily be made with impunity. This may be the explanation of the rarity of such abnormal cases in the whole family.

The attempts which I made, both in Plagusia and several of the other species of Flounders, to prevent the transfer of the eye by placing the glass dish at a height over a table, and thus allowing the light to come from below, as well as from all other sides, failed in arresting the transfer. This experiment, likewise, produced no effect in retaining the pigment spots of the blind side longer than in sj>eci- mens struck by the light only normally, from above.

The habits of young Flounders differ greatly from those of the adult : while the latter are generally more or less sluggish, the young Flounders, when measuring less than a couple of inches in length, are remarkably active, bounding through the water, as it were, and, if disturbed, frequently jumping out of the flat dishes in which I kept them. When this happened, falling from the table to the floor, they often remained a considerable time out of water, without appearing to suffer from their exposure, on being put back into water.

Giard has, in the Rev. des Scienc. Nat. for September, 1877, sug- gested that the fundamental cause of asymmetry in the animal king- dom was due to a difference in the strength of the organs of sense ; and he has given, in support of this view, some most ingenious speculations on the asymmetry of Ascidians, of which the Tadpole was transparent, while opaque Tadpoles belonged to symmetrical types ; the position of asymmetrical Ascidians being determined by

OF ARTS AND SCIENCES. 13

that of the organs of sense of the embryos. "We might add here, in favor of this view, the asymmetricals of many Acalephs (Hyboco- don), in which the disproportion of one of the organs of sense (tenta- cles) is very great. He further calls attention to the faets that, in Pteropods, it is the organs of sense which first show asymmetry, and suggests that cyclopism has been an indirect cause of restoration of symmetry; though this point does not seem well taken, — judging, at least, by what we know of the development of cyclopism among Crustacea. At any rate, the action of light upon organs of sense, which in all embryos are developed out of all proportion to their ulti- mate conditions, must remain an all-important element in its effect upon the nervous system. In embryos so transparent as many young fishes, which seem to be nothing but eyes, brain, and notochord, the action of light must be infinitely more potent upon the nervous system than it can possibly be in older stages, when the muscular system has obtained a so much greater preponderance. The sensitiveness of young fishes to the slightest disturbance of the water, either as a shock or from light, is exceedingly acute ; while, when older, they are appar- ently insensible to the same causes.

I have nothing to add to the explanation of the mechanism of color- ation given by Pouchet in his admirable memoir on the change of coloration, to which I have already referred. A recapitulation of the important points may, however, help the reader not familiar with his memoir to understand the changes taking place during the develop- ment of our young Flounders. In the coloration of fishes, we must distinguish colors due to interference of light produced by the presence of thin plates, and those due to anatomical elements frequently highly colored, and endowed with sarcodic movements capable of marked changes of form, under special influences, so as to present the shape of extended dendritic surfaces or minute spherical masses through which the pigment is distributed. The changes of coloration due to thin plates are, of course, exceedingly variable, the tints following each other with great rapidity, according to the angle at which we view them. Such lamellar coloration is common among insects, Crustacea, and also in some families of fishes. Among the most beautiful examples are those of the dolphin ( Goryphcena) and of Saphirina ; while the second class of colors — those due to the movements of the anatomical elements — are directly connected with the impressions of color received by the eye, and brought about by the reflex action of the nervous system. That this is the case, the rapid change of coloration produced by placing Flounders upon differently colored bottoms sufficiently proves. This

14 PROCEEDINGS OP THE AMERICAN ACADEMY

has, of course, a direct bearing upon the question of mimicry ; but it must be frankly stated that, as far as the causes of coloration among ani- mals have been studied, it is difficult to see how natural selection can have been a factor in producing permanent mimicry ; while the rapid- ity with which many fishes adapt themselves to the color of the bottom upon which they live enables them undoubtedly to produce a protective coloration, which is of advantage to them ; and constant habit may develop unequally the capacity of producing certain tints, or patterns even, which in their turn may be transmitted, and thus readily account for the lighter coloring of Flounders living upon sandy bottoms, as com- pared with those living upon rocky bottoms covered with dark algae. Yet place the latter upon a light ground and the former upon a dark ground, and they will very soon adopt the proper coloration of their bottom, showing they have not lost their power of changing. As for many of the patterns of coloration of birds and in insects, produced by physical causes, it seems quite impossible to look upon them as the fortuitous product of the action of light, or to regard it as an efficient cause of protective mimicry.

The pigment cells appear early in the egg. In some of the fishes, we have even two color elements in the older stages, immediately before the young fish is hatched, — viz., the black and yellow ; but, in the majority of cases, the black alone is present, the yellow element ap- pearing subsequently, and, last of all, the red. The experiments made by Pouchet on pigment elements show that the blue pigments are probably only a dimorphic condition of the red pigments. This would give a ready explanation why Lobsters turn red when cooked, and of the blue Lobsters which are occasionally caught. The same may also be said of green. Violet pigment, which is found in some Crustacea, gives special reactions.

The anatomical elements containing the pigment are greatly changed during growth. The examination of the pigment spots of the young- est fish on any of the Plates here given with more advanced stages shows how great is the capacity for expansion in the black pigment ele- ments, which from mere dots have almost become special organs capable of great expansion and contraction. Pouchet calls the pigment ele- ments chromatoblasts in their embryonic condition, to distinguish them from the chromatophores into which they eventually develop. In addition to the chromatoblasts and chromatophores, Pouchet has also called attention to a third set of bodies, which he calls iridocytes. These are found in Fishes, Reptiles, Mollusks : they are situated near the surface of the integument, and produce the phenomena of iridescence

OF ARTS AND SCIENCES. 15

of coerulescence by interference of light (as shown by Briicke), of solid particles more or less analogous to excessively thin laminae. By simple combinations of the action of the red, yellow, and black chro- matophores with the iridocytes are obtained all the colors which we can produce in Fishes, Reptiles, Crustacea, Mollusks, &c. ; these colors re- sulting mainly from the expansion near the surface, or retraction into an inferior layer of the black chromatophore, which, thus mixed with the yellow and red, or with the iridocytes, at greater or less depths, suffice to produce all the variations of coloring of our young Flounders. An examination of Plate VIII., showing the changes of coloring pro- duced upon young Flounders when placed upon differently colored bottoms, will readily show the process by which the different colora- tions are produced.

In the Flounders, after the eyes have passed to one side, the connection between the impression produced on the retina and the blind side becomes less and less distinct, until eventually a complete paralysis of the nerves affecting the chromatophores takes place ; and little by little the blind side thus becomes white with advancing age.

The pigment cells are of three colors, — black, yellow, and red (PL VIII. fig. 6) : the black expand nearest the surface, the yellow and red varying greatly in their position, according to the species. The black cells are all more or less dendritic when expanded, concentrating to a mere dot when wholly contracted. The proper mixture of the three colors in various degrees of expansion or contraction, combined with the suitable pattern of position, enables the Flounders to imitate so admirably the general effect of the ground upon which they are accustomed to feed, be it either sandy, gravelly, or muddy. So true is this, that often only a most practised eye could detect them, as, with the head slightly raised, the eyes starting out of their sockets far above the surface of the head, they turn actively in all directions, seeking for prey, or trying to escape the notice of their enemies. The rapidity with which they produce this change of color is quite striking ; and, although it was well known that many fishes had the power to change gradually the tint of the body, it had not been noticed that it could be effected rapidly, and apparently at will, before it was recognized by Pouchet. I have not unfrequently removed the jar containing a young Flounder (PI. VIII. fig. 2) from a surface imitating a sandy bottom to one of a dark chocolate color, and in less than ten minutes I have seen the black pigments obtain such a preponderance (PI. VIII. fig. 1) that it would hardly have been possible to recognize in the dark, almost black fish the young Flounder, whose yellowish-gray speckled

16 PROCEEDINGS OF THE AMERICAN ACADEMY

hue had so well simulated sand, a few moments before. On removing him to a gravelly bottom, the spots of the side quickly became promi- nent (PL VIII. fig. 3). During all this time, the pigments of the blind side showed no trace of any sensitiveness ; while, if these ex- periments are made when the eyes are still on both sides, the pigments of the two sides change at the same time in a corresponding manner.

It is well known that Squids and Cuttle Fish, provided as they are with exceedingly sensitive chromatic cells, are also able to imitate, for their protection and disguise, the coloring of the ground upon which they happen to live. But, in Cephalopods, the change of color of these chromatophores is more intimately connected with the nervous sys- tem, and appears far more sensitive and less subject to control than among fishes. In Cephalopods, the mere act of moving the mantle, of breathing, or of forcing the water through the siphon, seems sufficient to produce a change of tint ; and a sudden disturbance is as likely to bring about a detrimental as a beneficial change of color.*

Among Fishes, Reptiles, and other Vertebrates, as well as among Ce- phalopods, and the mass of Mollusks, Crustacea, Annellids, Echinoderms, &c, in which we find dermal pigment cells, we can readily imagine how the effect of environments might, by reflex action, bring about a resemblance to surrounding coloring, as has been described by Pouchet and by Bert, thus producing general effects in the pigment cells, which would assimilate within certain limits with the surrounding tone. In all these cases, the explanation based upon mimicry as bene- ficial presents little difficulty ; and we might suppose that by the laws of heredity those colors alone which had been stimulated by continued action through many generations would be transmitted. Thus Flounders, for instance, living on sandy bottom, in which the grayish tint imitating sand had been most constantly produced by the action of the proper pig-

* See the papers on the chromatophores of Cephalopods, by Huhrecht, Niederland. Archiv f. Zool., II. No. 3, p. 8, Mai, 1875, in which he makes a most interesting comparison of the phenomena of chromatophores and protoplasmic action. Also an important paper by Dr. Hagen, in the American Naturalist, vol. vi., July, 1872, on mimicry in the color of insects. The general results of Dr. Hagen's study of the phenomena of color in insects agree, in the main, with the results obtained by Pouchet from the study of Fishes, Crustacea, and Mol- lusks ; both Pouchet and Hagen recognizing the presence of colors due to action of light, and the presence of colors due to pigments, the hypodermal and dermal layers. Judging from the interesting discussions brought out by the papers of Weismann, of Wallace, and others, on the causes of color in the animal kingdom, we are, however, only on the threshold of a most interesting and novel field of inquiry.

OF ARTS AND SCIENCES. 17

ment cells, would naturally transmit to their progeny in the greatest quantity only such pigment as would most easily reproduce the imita- tion of sand, while the same might he true of the Flounders living on muddy or gravelly bottoms. Something analogous exists in the common Echini, where dark-green and violet pigment spots closely imitate dark granitic rocks covered with seaweeds ; or in the imitation of sand by the grayish-green tint of Mellita and the yellow tint of Am- phidetus, &c. : yet the whole theory of mimicry, even in these cases, as a means of protection, is again overthrown by the mass of Clypeas- troids, Spatangoids, Echinoids, whose dark coloring, but for their habit of burrowing in the sand in which they live, would make them most prominent objects. We next have the legions of Ctenophorse, Jelly Fishes, and of other pelagic animals (especially the embryos) so trans- parent as to be scarcely distinguishable from the water in which they live, many of them are reduced to the merest film. Have they all, little by little, assumed their transparency, in order to escape their enemies ? Then why do they swarm in such quantities that their numbers counteract the very object of their transparency ? It is common along the seashore, at proper times of tide and wind, to find long lines where all these delicate and transparent animals are accumulated on purpose as it were to provide the food needed by their enemies, who are at hand playing sad havoc among them. Many of the embryos of our com- mon marine animals are gregarious for a short period of their life ; for instance, the young of the majority of our Crabs and Shrimps, of many Gasteropods, Annellids, and Radiates, just at the time when they are most delicate, and least capable of escaping the attacks of their enemies. At the time of hatching of the young Prawns (Palcemonetes vulgaris), and of the young of our Cancer, sea perch may be seen devouring them by the wholesale while they are swarming close to the shore. Thus, numberless young are destroyed in spite of their transparency, and the same holds good for a host of other embryos.

In the Flounders, we seem to have fair evidence that they are able to produce certain effects in consequence of impressions received upon the retina, and that the changes taking place on the chromatic side of the body are probably due to the capacity of the fish to distinguish cer- tain colors from others. But more accurate experiments than I have yet made are necessary to enable us to decide whether the sense of color is developed so early in the Vertebrate series, or whether we have simply a set of reflex actions. It certainly seems, from a physiological point of view, very hazardous to infer — as has been frequently done on philological grounds — the gradual development of the sense of vol. xiv. (n. s. vi.) 2

18 PROCEEDINGS OP THE AMERICAN ACADEMY

color in early races of mankind, from the color descriptions of Homer and early Greek writers. It is not an uncommon thing to find chil- dren of the lower classes unable to give specific names to the different colors ; but, if I am not mistaken, they can always distinguish the primary colors without difficulty, though not able to name them. Cer- tainly, the facility for painting and coloring noticeable in the pottery of the uncivilized races of the world seems unfavorable to this theory.

EXPLANATION OF THE PLATES.

The Plates accompanying this paper are a fair sample of the results to he ohtained from the transfer of original drawings by the Heliotype process. The drawings are quite acceptable reproductions of the originals ; and this method of illustrating papers on Natural History will prove very useful in many cases. The method described by the younger Sars for obtaining transfers from original drawings is somewhat cumbersome, requiring a great deal of care and a num- ber of processes. The present method simply requires for the naturalist that he should put on thin Bristol board the plate he desires to have transferred, of the size he wishes, and arranged as he desires ; the only requisite being that the figures be all drawn with a pen and with a special ink. He may then be assured that he will get a plate nearly as clear as his original ; and several transfers being made from the original, — say three or four, — a large number of clear copies can be struck off without reducing the distinction of the im- pressions, as is invariably the case in all lithographic processes. The delay incident to all lithographic processes requiring a special artist are done away with, and the author has only himself to blame for errors. This method seems to give better results than that employed by Sars. Compare his plates of Brisinga with those of the present paper. The cost of the Heliotype method is moderate ; the impression on paper, and whole manipulation, after the drawing is supplied to the patentees of the process, being considerably less than the cost of printing and paper from an ordinary lithographic stone.

Plates III., IV., V., figs. 1-5, illustrate the development of a dextral Flounder, in which the eye passes from the left side to the right side.

Plate V., figs. 6-13, Plate VI., illustrate the development of a sinistral Flounder, in which the eye passes from the right side to the left.

Plate VII. illustrates the development of a sinistral Flounder, in which the eye passes from the right to the left side long before the dorsal, anal, or caudal fins have lost their embryonic character.

Plate VIII. illustrates the changes of color produced in the young Flounders by placing them on differently colored ground.

Plate IX. shows the development of a sinistral Flounder, in which the ante- rior part of the dorsal becomes to some extent an anterior dorsal.

Plate X. illustrates the passage of the eye through the integuments between the base of the anterior part of the dorsal and the frontal bone.

OP ARTS AND SCIENCES. 19

PLATE in.

Pleuronectes Americanus Walb.

Platessa plana Storer PI. XXX. fig. 2.

Fig. 1. Young, about 4mm long a few days after hatching. Seen from the left side. The eyes are symmetrically placed at the extremities of an axis at right angles to the longitudinal axis. The pectorals are well developed, the embryonic fin extends unbroken from the base of the brain to the anus, the ventral portion is somewhat broader. The eyes are of a light bright-green, and there are faint yellow patches on the lower sides of notochord along the muscular bands.

„ 2. Somewhat older than fig. 1. The tail has become slightly hetero- cercal, and the embryo is much less transparent than in the previous stage. The muscular tissue above and below the notochord is of a light-brown color, with yellow patches near the black pigment spots. One or two very indistinct tail-rays have begun to form.

„ 3. In this stage, the principal changes are confined to the increased num- ber of tail fin-rays, and to the segmentation of the vertebral column sending out its dorsal and ventral cartilaginous apophyses. The pigment spots of the embryonic fin-fold (fig. 1), as well as of other parts of the body, seem to become more prominent, when increased activity in the formation of new tissues takes place. See the pig- ment spots in the tail of this figure.

„ 4. A somewhat more advanced stage, in which the dorsal and ventral embryonic fold has become tolerably separated from the tail-fin. At the base of the dorsal and ventral folds, the basal fin-rays are well developed, but as yet we find no trace of the fin-rays proper.

„ 5. In this stage, the tail-fin is in great part separated from the embryonic fin-fold, which shows here and there traces of the formation of the fin-rays proper ; but in other respects it differs from the preceding stage mainly in the greater number of pigment spot patches, in the greater development of the muscular bands, and of the dorsal and ventral apophyses of the vertebral column. The eyes are as yet symmetrical. The length of this embryo is about that of the preceding stage (fig. 4).

PLATE IV.

Pleuronectes Americanus Walb.

Pig. 1. We now come to a series of stages in which the body becomes broader in proportion to the length, and in which the dorsal and anal fins are all gradually isolated from the caudal. In this stage, the fin- rays extend nearly to the edge of the dorsal and anal, the muscu- lar bands are much wider, and there is a slight asymmetry in the position of the left eye, which has moved well forward towards the top of the snout ; while in the preceding stages the left barely

20 PROCEEDINGS OF THE AMERICAN ACADEMY

extended to point of a vertical passing through the lower extremity of the upper jaw. The patches of color which are to be even- tually characteristic of the species first make their appearance in this stage. Fig. 2. Somewhat more advanced than fig. 1. The left eye, when seen from the right side, projects slightly in advance of the frontal. The dorsal and anal fin-rays are well developed, but still united to the caudal. The tail has become rounded. The patches of coloring are defined. Kudimentary ventral fins have appeared. There are as yet no hard rays in the pectorals.

„ 3. In this stage, the left eye has moved more towards the crest of the snout, the dorsal and anal fins are disconnected from the caudal, and the ventrals are larger than in the preceding stage.

„ 4. More than half the left eye is seen above the frontal ridge ; the dorsal and anal still more disconnected from the caudal than in the pre- ceding stage; the ventrals larger, and the pattern of coloration quite marked by prominent pigment cells.

„ 6. In this stage, the left eye has fully passed to the right side, the dorsal fin, extending to the upper edge of the orbit, having gradually extended in that direction from stages represented in PI. IV. figs. 2, 3, 4. The pattern of coloration of the body and of the fins is like that of the adult, but, of course, more indistinct. The dorsal and anal fins are now completely isolated from the caudal fin : they have both fin-rays fully developed, and have greatly increased in breadth since the last stages figured.

PLATE V.

Figs. 1-5. — Pleuronectes Americanus Walb.

Fig. 1. Head of a young specimen, about in condition of PI. III. fig. 1. Seen from above, to show the symmetrical portion of the eyes.

„ 2. Head of another specimen, about in the same stage as in fig. 1. Seen from below.

„ 3. Head of a young specimen somewhat more advanced, in which the left eye has changed its position somewhat, and has advanced towards the snout ; showing the effect, when seen from above, of the first movement of translation of the eye of the left side.

„ 4. Head of young Flounder, intermediate between figs. 4 and 5, PI. III., to show the transfer of the left eye above the ridge of the frontal bone.

„ 5. The head of a young Flounder, nearly in the same condition as fig. 4. Seen from the left side, showing the position of the eye during the transfer while projecting above the frontal bone.

Figs. 6-13. — Pseudorhombus maculatus Stein.

Fig. 6. Head of young specimen still in the egg. Seen from above. The eyes symmetrically placed at extremity of a transverse axis at right angles to the longitudinal axis of the Flounder.

OF ARTS AND SCIENCES. 21

Fig. 7. Head of same species, a couple of days after hatching, before any movement of translation or of rotation of either eye has com- menced. The two eyes symmetrically placed at the extremities of a transverse axis at right angles to the longitudinal axis of the Flounder.

„ 8. Shows the position of the eyes of the young Flounder from the left side, where the right eye projects beyond the ridge of the frontal bone.

„ 9. Shows the position of the right eye, seen from the right side, at about the time the lower edge of the orbit has reached the summit of the edge of the frontal bone.

„ 10-13. Show in regular succession the gradual passage of the eye from the stage of fig. 9 until it has reached, in fig. 13, the position it re- tains on the adult entirely on the left side of the body ; the space between the eyes separated by the frontal ridge becoming less in each specimen with advancing age.

PLATE VI.

PSEUDORHOMBUS MELAHOGASTER STEIN. MASS. FlSH Rep. 1872, p. 47.

Platessa oblonga Storer PL XXXI. fig. 2.

Fig. 1. Young specimen, just hatched from the egg. The yolk mass project- ing below the outline of the lower surface ; the dorsal embryonic fold much wider than the anal embryonic fin ; the pigment spots are confined to the dorsal edge of the brain, and to the muscular band above the notochord.

„ 2. Embryo two days old. The yolk mass projects but little beyond the line of the lower surface. Large prominent pigment spots extend over the whole body, with the exception of a small portion of the tail, which is left bare from the earliest stages (fig. 1), and remains bare for some time yet, thus giving an excellent specific distinction for readily distinguishing the young of this species from other species of embryos about in the same stages. The snout has become more pointed than in the preceding stage, the dorsal embryonic fold has lost much of its width, and in consequence the young fish resembles a tadpole much less than in the preceding stage.

„ 3. Represents the same embryo on the fifth day after hatching. The prin- cipal changes consist in the form of the head, the prolongation of the lower jaw well in advance of the upper one, the presence of large pectorals, the increase of the stomach, and a very slight tendency to heterocercality in the tail.

„ 4. Somewhat older embryo. The stomach and alimentary canal have greatly increased in size, the air-bladder has become prominent, the body has greatly increased in width, the tail is decidedly more heterocercal than in the previous stage figured, and the right eye shows a slight tendency to move upward and forward towards the anterior edge of the snout.

22 PROCEEDINGS OF THE AMERICAN ACADEMY

Fig. 5. In this stage, considerably larger than the previous one, the change in the outline of the young fish is considerable. The dorsal is highest at its anterior extremity, the caudal is well separated from the dorsal and anal fins, in all the fin-rays are fully formed, the profile of the head is more blunt, and the whole body thickly covered with dark pigment cells.

„ 6. The differences of this stage from the younger one (fig. 5) consist mainly in the greater width of anterior part of the body ; the dis- tinct pattern of coloration ; the increase in width of the dorsal and anal fins, and their disconnection from the caudal, which has be- come elongated and rounded at the extremity ; the presence of small ventrals ; and the transfer of the right eye forward and up- ward, so that one half is visible above the frontal from the left side.

„ 7. Is a young Flounder, taken late in the season, but slightly larger than fig. 6, in which, however, the right eye has passed well over to the left side. The dorsal has extended towards the posterior edge of the right eye, its anterior edge projecting over the eye. The pattern of coloration is similar, in a general way, to that of the adult, and extends into the base of the broad dorsal and anal fins. The ven- trals are larger than in fig. 1. The Flounder in this stage and the preceding stages (figs. 4, 5) habitually rests on the right side, but as yet none of these young fishes show any difference in the color- ation of the right from the left ; the former being still quite as brilliant as the latter in the oldest stage here figured (fig. 6).

PLATE VII. Rhombus maculatus Mitch.

Pleuronectes maculatus Storer PI. XXXI. fig. 4.

Fig. 1. Young ^specimen, with rudimentary air-bladder, few pigment spots, measuring 5mm in length.

„ 2. Somewhat more advanced than fig. 1. The pigment spots greatly de- veloped, but the embryonic dorsal and anal fins show scarcely any advance.

„ 3. The body has become somewhat broader, the tail far more heterocercal, and rudimentary fin-rays appear both in the dorsal and anal fins. Patches of coloring indicating the future pattern are well defined.

„ 4. Somewhat more advanced, but slightly longer, than fig. 3. The base of the fin-rays of the dorsal and anal are well developed. The body, with the exception of a bare space of the tail and adjoining part of the body, is of a uniform grayish-brown color, with patches of yel- low, and black longitudinal lines along the upper and lower edges of the notochord, and the base of the dorsal and anal fin-rays, as well as following the muscular bands along the ventral edge. The upper and posterior edge of the stomach is covered by intensely black pigment spots closely crowded together.

OP ARTS AND SCIENCES. 23

Fig. 5. Slightly older than the preceding stage. The eye, from the right side, projects ahove the line of the snout; the coloring much as in fig. 4. The anal, dorsal, and caudal fins are, however, more advanced.

PLATE VIII.

Rhombus maculatus Mitch.

Fig. 1. Young sinistral Flounder, natural size, showing the color assumed when the fish is placed upon a dark mud-colored ground.

„ 2. The same fish, somewhat enlarged, showing the coloring assumed when placed upon a yellowish sandy soil.

„ 3. Another specimen of the same species, somewhat younger than the preceding stages, showing the coloring assumed when placed upon a mottled ground (partly gravel, partly sand) somewhat darker than the yellowish sandy soil.

„ 4. Black pigment spots forming the blotches along the lines of the rays of the dorsal, when fully expanded.

„ 5. Another portion of the dorsal, showing the spots when contracted.

„ 6. A portion of the pigment spots of the colored side, showing the red, the yellow, and the black pigment spots when fully expanded, the darker tints between the colored pigments representing the masses of iridocytes.

PLATE IX.

PSEUDORHOMBUS OBLONGUS STEIN.

Platessa quadrocellata Storer PI. XXXI. fig. 3.

Fig. 1. Egg of Flounder, showing the symmetrical head of embryo. „ 2. Head of young Flounder, the fourth day after hatching. Seen from

above. „ 3. Head of fig. 4. Seen from below. „ 4. Young Flounder. Seen in profile. Quite transparent. Remarkable for

the great development of the dorsal embryonic fin, 6.5mm in length. „ 5. Somewhat older than fig. 3. First trace of heterocercal tail. „ 6. Older than fig. 4. The anterior part of the dorsal is developed before

the rest, forming a sort of anterior dorsal. The eyes are still

symmetrical. „ 7. Young Flounder, quite well advanced. The fins are all differentiated.

The right eye has, however, moved, thus far, but little forward and

upward.

PLATE X.

Plagusia Sp.

Fig. 1. Young Plagusia, slightly over an inch long. Seen in profile. The eyes of the two sides are equally distant from the snout : they are placed symmetrically with reference to a longitudinal axis, and a plane

24 PROCEEDINGS OF THE AMERICAN ACADEMY

passing through the transverse axis. This specimen is perfectly transparent, — fully as transparent as the most delicate Hydroid Medusa. The action of the heart, the course of the vessels, can be readily followed, as well as the other structural details, which are usually only visible after dissection. The dorsal fin projects far down the frontal ridge to the nostrils, well in advance of the eyes. Fig. 2. Young Plagusia (fig. 1). Seen with head on.

„ 3. Shows the relative position of the eyes after the first movements of translation and of rotation have become visible by the slight advance and rising of the eye of the right side. Seen from the left side.

„ 4. Somewhat more advanced than fig. 2. Seen from the right side. The outline of left eye can be traced through the tissues of the head.

„ 5. Head, seen from the left side. The right eye has moved upwards suffi- ciently to be seen through the tissues of the head, clear above the left eye. We find in this stage the first trace of the opening of the eye on the left. The eye, when turned in the socket, can look through the tissues at the base of the dorsal; and, when thus turned, to see through the left, is nearly as sensitive to approach- ing objects as the left eye. When looking at the same fish for the other side (the right), we find that the eye has deeply sunk in the tissues between the frontal bone and base of dorsal fin, and that, while sinking and pushing its way to the opposite side, the tissues of the right side have gradually united and narrowed the former large circular orbit to a mere small elliptical opening.

„ 6. The eye of the right side, as turned to the right ; the new orbit ap- pearing on the upper edge of the eyeball.

„ 7. The same eye with the ball turned toward the left, showing the com- mencement of the new orbit forming as a small circular opening on the left side of the fish. The old orbit of the right side being now reduced to a minimum, the fish now having two orbits on the left side and one on the right. The orbit of the right being re- duced to a small aperture, and disappearing in a subsequent stage (fig. 9), while the new orbit of the right eye on the left side is as yet much smaller than the corresponding orbit of the left eye.

„ 8. Head seen from the right side, showing the small size of the old orbit of the right eye after it has forced its way partly across the head.

„ 9. The right eye has now passed entirely round the frontal bone, and is held in its hollow curve, and has at same time forced its way through the tissues so far that the original orbit of the right side has become closed, and the new orbit for the right eye on the left side has become nearly as large as the orbit of the left eye.

„ 10. In this stage, the eye from the right side is now completely trans- ferred to the left, and no difference is apparent between the orbits. In this and all preceding stages, the great length of the two optic nerves is readily seen ; and we thus understand the possibility of so extensive a movement of either eye without interfering with the visual function. The slack of the optic nerves being only taken in for the eye which happens to be transferred in any genus of Flounder.

OF ARTS AND SCIENCES. 25

There is in Flounders a most active circulation going directly from the heart to the orbits and hack again : this is well shown in this figure by the direction of the arrows along the vessels leading towards the orbits and back again to the heart. Fig. 11. Is a young Plagusia, after the transfer of the eye, nearly three inches long, showing even at this stage but a slight accumulation of pig- ment spots along the dorsal and anal fins parallel to the line of the spines. A few yellowish and black pigment spots have also ac- cumulated on the left side, but the young fish has as yet lost but little of its transparency.

What eventually becomes of this species I am not able to say, and it is not improbable that this species is identical with that described by Steenstrup, and it may also be the young of the Plagusia found on the Atlantic coast of the Southern States.

PROCEEDINGS OF THE AMERICAN ACADEMY

II.

EXPERIMENTS UPON PIEZOMETERS USED IN HYDRAULIC INVESTIGATIONS.

By Hiram F. Mills, Civil Engineer.

Presented April 10, 1878.

In making experiments upon water flowing in pipes and in open con- duits, it is most convenient to measure its pressure against the side of the' pipe or conduit, and its depth in the conduit, by means of small tubes extending through the side, normal to its surface, and communi- cating with vertical columns of water, contained in glass tubes or in small reservoirs.

Such columns of water, used to measure pressure, are called piezometers.

The question has arisen : Do they indicate the actual pressure against the side of the pipe, of the water when in motion, or do they indicate the actual height of the surface of the moving water in the conduit ?

M. Darcy, in his great work * on the movement of water in pipes, says (page 217) : " Indeed, manometers do not indicate the entire head of a conduit at the points where they are adjusted, but this head diminished by a certain height, the diminution being due to the velocity of the fluid at the base of the piezometers : the water, by its cohesion, acts upon the manometric column, whose height it lowers."

Again, he says : " When one of the manometers was placed upon the cylindrical reservoir, where the velocity of the fluid was very slight relatively to that of the water in the pipe, we see that in like circum- stances the lowering by suction of the manometer upon the reservoir should be less than the lowering by suction of the manometer upon the pipe. . . . There was then a rectification to be made, but I have not at this time the means of making it. In the experiments relative to open canals, with which I am now occupied, I shall seek to determine

* Recherches Experimentales relatives au Mouvement de l'Eau dans les Tuyaux. Par Henry Darcy, Inspecteur-Ge'neral des Ponts et Chausse'es. Paris, 1857.

OP ARTS AND SCIENCES. 27

the law followed by these lowerings, according to the diameter of the orifice in communication with a current, and according to the velocity of the latter."

In the published records of the experiments relative to open canals,* the results here anticipated are not included, and we are not informed of the later conclusions of this able engineer.

In the performance of my duties as engineer of the Essex Com- pany, — a company controlling the water power of the Merrimack River at Lawrence, Mass., — it has become important to interpret with accuracy the indications of piezometers, and to determine the circumstances affecting their reliability. To this end, a long series of experiments has been made upon piezometers, having orifices of com- munication of varying size and form, and through a wide range of velocities. The results of these experiments are regarded as of impor- tance to investigators in hydraulics, and are, through the liberality of the officers of the Essex Company, now presented for their use.

It is well known from the experiments of Venturi f that within a short distance from the entrance of a pipe — a distance limited by the influence of the contraction at the entrance — piezometers indicate a pressure varying with their position, and widely different from that which obtains after the section influenced by contraction is passed. These phenomena are readily explained without attributing any dis- crepancy between the pressure upon the sides of the pipe and the indications of the piezometer. It is now, however, only necessary to consider that portion of the pipe or conduit in which uniform motion is established ; that is, a portion in which the particles of water move parallel with the sides of the pipe with a velocity neither increasing nor decreasing.

Uniform motion then existing, the prominent facts to be determined are whether the height of the piezometric column is lowered by the cohesion of the water acting at the base of the piezometer or not ; and whether or not the height of the column of still water indicates with accuracy the height of the surface of the adjacent mass of moving water in an open conduit.

* Recherches Hydrauliques, entreprises par M. H. Darcy, Inspecteur-General des Fonts et Chaussees : continuees par M. H. Bazin, Ingenieur des Ponts et Chaussees. Premiere Partie : Recherches Experimentales sur l'Ecoulement de l'Eau dans les Canaux de'couverts. Paris, 1865.

t Tracts on Hydraulics. Edited by Thomas Tredgold, C. E. II. Venturi's Experiments on the Motion of Fluids. Second Edition. London, 1836, page 136 et seq.

28 PROCEEDINGS OP THE AMERICAN ACADEMY

For determining these facts, the apparatus represented upon plates No. 1 and No. 2 was constructed. It consisted of a straight trough thirty feet long, of uniform section, one foot deep and three-tenths of a foot wide inside, receiving water at A from a chamber four feet wide. At a distance of six-tenths of a foot up stream from the entrance was a gate B, which, being opened, connected the chamber with a penstock four feet wide, six feet high, and two hundred feet long, bringing water from the Essex Company's south canal. The down-stream side of the chamber A was built up to the height required during the several experiments ; and its upper edge used as the crest of a regulating waste weir, over which water continually flowed into the waste trough C, which conducted it outside of the measuring basin.

The experimenting trough discharged its water at D into the swing- ing conductors, supported by the pivot a, which conveyed it by the branch E directly down into the measuring basin G, or by the branch F into the river, as the partition b was raised above or lowered below the stream.

The measuring basin G, 15.93 ft. wide, and 36.55 ft. long, and about 8 ft. deep, built of timber and planks on a firm foundation, was buried in earth nearly to its full depth, except on the river side, which was held from being pressed outward by a strong truss ; and except at the observer's house H, where the heights of water in the basin were observed.

The area of the measuring basin, within the range of filling during the experiments, which was between 4.5 ft. and 6.5 ft. above the bot- tom, was, deduction being made for all supporting timbers for the upper works, found to be 570 square feet.

The depths of water in the measuring basin were measured by means of a hook gauge in the box c, which was in free communication with different parts of the basin by three pipes, 0.083 ft. in diameter.

The hook gauge used is described and illustrated in " Lowell Hydraulic Experiments," * page 18.

Water was drawn from the measuring basin through the waste gate d.

The experimental trough was at first placed level, having firm bear- ings about ten feet apart. The upper end was connected with the chamber A with a lining of rubber, making a water-tight joint, which continued water-tight when the other end of trough was lowered

* Lowell Hydraulic Experiments. By James B. Francis, C. E., &c. Third Edition. New York : D. Van Nostrand. 1871.

OF ARTS AND SCIENCES.

29

through its successive steps to increase the velocity of the water passing through it.

Starting four feet from the entrance, cross bars of wood 0.9 ft. long, 0.1 ft. wide, and 0.15 ft. deep, were screwed to the top of the trough at intervals of just 2.5 ft., the top of the trough being let up into them 0.05 ft.

The up-stream top edge of each cross bar was taken as a station, and these were numbered from 1 to 1 1, beginning with the up-stream cross bar.

Under the projecting ends of the cross bars were attached, to the outer surface of the two-inch planks which made the sides of the trough, tin boxes about 0.9 ft. long, 0.5 ft. wide, and 0.9 ft. high, hav- ing blocks of wood fastened within some of them, as shown upon the plates, to reduce the free surface area of water which they would con- tain. These boxes, serving as reservoirs, and called still-boxes, were put in communication with the interior of the trough by passages hav- ing orifices of various forms and dimensions, and being variously dis- posed, as expressed in the following table : —

Number of Station.	Side of Trough.	Form of Orifice.	Distance of centre up stream from Station.	Distance of centre above bottom of Trough.	Diameter or Dimensions of Orifice.	Angle of passage with inside of Trough.	Material border- ing Orifice.
			Feet.	Feet.	Feet.
2 2	West. East.	Circle.	0.045 0.062	0.333 0.333	0.043 0.043	48° up stream. 48° down stream.	Brass.
3 3	West. East.	Circle.	0.057 0.054	0.421 0.497	0.052 0.086	90° 90°	Iron. >i
4 4 4 4	West. East.	Circle.	0.059 0.058	0.249 0.422 0.249 0.411	0.010 0.083 0.042 0.021	90° 90° 90° 90°	Wood. ?»
5 5	West. East.	Rectangle. >i	0.052 0.052	0.505 0.500 4	0.084 wide. 0.337 high. 0.021 wide. 0.336 high.	90° 90°	Wood. u
6 6	West. East.	Circle. i>	0.054 0.083	0.333 0.333	0.021 0.021	30° up stream. 30° down stream.	Brass.
7 7	West. East.	Ellipse.	0.050 0.053	0.417 0.420	0.030 long. 0.021 high. 0.030 long. 0.021 high.	45° up stream. 45° down stream.	Wood. ii
8 8	West. East.	Circle. ii	0.052 0.052 0.052 0.052	0.255 0.420 0.333 0.502	0.021 0.042 0.010 0.083	90° 90° 90° 90°	Wood.
9 9	West. East.	Square. Rectangle.	0.053 0.053	0.500 0.336	0.167 0.334 long. 0.083 high.	90° 90°	Wood.
10 10	West. East.	Ellipse. it	0.053 0.054	0.334 0.334	0.042 long. 0.021 high. 0.042 long. 0.021 high.	30° down stream. 30° up stream.	Brass. »i

30 PROCEEDINGS OF THE AMERICAN ACADEMY

The water flowed toward the north. Distances indicating position of orifices were measured when the trough was level.

The trough with its appurtenances heing in place, the whole was covered with a house about eight feet wide and ten feet high, having windows at the top.

The comparative heights of the water surface in the stream and in the reservoirs adjacent were now to be determined. The first step was to measure the heights of three points at each station — one over the middle of the stream, and one over each of the still-boxes — above a surface of still water. This was done by the aid of three kinds of instruments. The first kind, by which any change in height of the water surface was noted, consisted of a plate of brass placed horizon- tally, through which projected vertically upward fifty-one steel nee- dles in two rows. The first needle being finished with its point just 0.1 ft. above the bottom of the plate, and the fifty-first having its point 0.11 ft. above the same surface, the intermediate points being sepa- rated by equal spaces, were finished to be in the same inclined plane with the extremities ; hence each point was 0.0002 ft. higher than the next lower.

Six other needles, rising above these in another row, indicated the position of the points reading two-thousandths.

The second kind of instrument consisted of a rod having a scale divided into hundredths of a foot, sliding along a short standard hav- ing a stationary vernier reading to thousandths, by which distances of two ten-thousandths of a foot could be readily distinguished. The rods were held in a vertical position by fitting into frames above each point of observation. They were terminated at the lower end by a long finely pointed needle, which was brought in contact with the water surface.

The third kind of instrument consisted of a vertical micrometer screw, piercing a horizontal iron plate which made a part of its nut, and whose under surface was kept level by a level bulb upon its upper surface. The screw was terminated below with a finely pointed nee- dle, and above, near the head, was supplied with an index, whose position was read upon a circular scale made upon the top of the nut, in which one ten-thousandth of a foot was indicated by the space of about one one-hundredth of a foot.

After determining by these instruments the actual heights above a datum plane of all of the points where observations were to be taken, the same instruments were used upon the same points for determining the heights of the water surfaces, when water was flowing through the trough.

OP ARTS AND SCIENCES. 31

During experiments with mean velocities less than three feet per second, the trough was maintained in its level position, and the height of surface and velocity were regulated by screwing a steel plate to the lower end of the trough at the proper height, thus discharging the water over a weir. With greater velocities, the plate was removed, and the trough was more or less inclined.

During experiments, the measurement of the quantity of water flowing through the trough was continuous, interrupted only by draw- ing water from the measuring basin.

Generally there were as many as four observers, with their instru- ments, making simultaneous observations at as many stations, with assistants to record their reading.

Upon experimenting with velocities greater than three feet per second, the disturbance at the entrance was found to continue past Station No. 1, consequently all the observations at this station are omitted.

At stations numbered from two to ten inclusive, 5925 observations were made upon the height of the different water surfaces, with veloci- ties in the trough from about 0.6 ft. to about 9 ft. per second. These observations have been divided into 518 experiments, giving a series of heights in each still-box above the surface of the stream at the respective stations. These experiments have been grouped, by put- ting together those at each station in which the mean velocity and depth of water in the trough were nearly constant, and taking the mean of the heights of the water in each still-box above the surface of the stream. These mean results for each velocity, together with the depth of water, the number of observations, and number of experi- ments included in each result, are given in the following tables, and are followed by columns of corrected results, which are described in the headings : —

32

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OF ARTS AND SCIENCES.

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PROCEEDINGS OF THE AMERICAN ACADEMY

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OF ARTS AND SCIENCES.

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	0«rtrtlO»t-«00

38 PROCEEDINGS OP THE AMERICAN ACADEMY

The following notes were made at Station No. 4, when the mean velocity of the stream was eight feet per second : —

10h 9'. There is a depression in surface of stream about 0.5 ft. below Sta.

No. 3 ; and a swell at 0.85 ft. above Sta. No. 4. Distance from

swell to depression, 1.15 ft. 11'. Depression 0.3 ft. below Sta. No. 4, and swell 1.3 ft. below Sta. No. 4.

Distance, 1 ft. 12'. I should judge that the swell above Sta. No. 4 is about 0.02 ft. above

the line connecting the depressions.

The depression and swell move longitudinally, frequently about

one-half a foot, and more rarely to the extent of replacing each

other. 22'. There is continual change in height of surface, but noticeable fluctu- ations come as often as three-quarters of a second, and from 0.01 ft.

to 0.02 ft. in height. 34'. There is a swaying of the highest part of the stream from side to side ;

generally from within a tenth of a foot from one side to a tenth of

a foot from the other, but occasionally running nearer the side. 30'. There are times when the surface is quite even from side to side,

and again it will vary as much as 0.02 ft. 3S7. A swell longitudinally follows this fluctuation from side to side, but

is not a swell the full width of the stream. 39'. The swell seems to be a twisting of the thread of the current from

one side of the trough to the other. 4F. In the cross section there is a rise of the surface on each side, and a

rise of the thread of the stream tor a width of about 0.00 ft., and

a depression each side of this.

Immediately after the ahove observations, the following were made at Station No. 8, in the midst of the series of eleven experiments, having a mean velocity of 8.39 ft. per second.

10h 46'. The longitudinal distances between the swells and depressions are

greater near Sta. No. 8 than at Sta. No. 4, but are less definite.

The variation in height is at times as much as 0.02 ft. 52'. The surface of the stream is much more even here than at Sta. No. 4.

There is no marked rise near the middle of the stream, but there

is a swaying of the highest part of the stream from side to side

about 0.01 ft. 64'. The line of air-bubbles is nearly obliterated, varying to 0.04 ft. each

side of the middle, but most of the time remaining on the east side

of the middle.

Orifices in the Plane of Side. Passages normal.

The results obtained with orifices whose edges do not vary percep- tibly from the plane of the side of the trough, with passages normal to this plane will first be considered. Such are found on both sides at Station No. 4, on both sides at Station No. 8, and on the east side at Station No. 9.

OF ARTS AND SCIENCES.

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40 PROCEEDINGS OF THE AMERICAN ACADEMY

Combining the results obtained at these orifices, grouping those made at the same time or under like circumstances, and giving to each a weight proportioned to the number of observations from which it is obtained, we have the general results contained in the foregoing table.

These average heights are represented in Fig. 1, Plate No. 3. In this Plate and in Plate No. 4, the horizontal lines represent the sur- face of the stream ; the ordinates are the heights expressed in full scale or in actual distances above and below this surface ; and the abscissas are mean velocities, in which one foot per second is expressed by one twenty-fourth of a foot.

Taking a general view of these average heights, we find five results are positive and six are negative ; and the general average height of all, or the sum of the products of each height multiplied by its num- ber of observations, divided by the whole number of observations, gives for the 1440 observations, the height of the surface of water in the still-boxes, 0.0007 ft. above that of the surface of the middle of the stream.

Examining more in detail, we find that, with mean velocities up to four feet per second, the heights of the surfaces in the still-boxes and those at the middle of the stream coincide, within the practicable limits of measurement. With velocities from five feet to nearly nine feet per second, the heights of surfaces in the still-boxes are both above and below those of the middle of the stream by measurable quantities.

If we now assume, for the purpose of comparison, that, if there is any real difference in these heights dependent upon the velocity, it will vary with the square of the velocity ; and assuming also that the incessant fluctuations of the surface of the stream vary in height with the square of the velocity of the stream, it will be found by plotting these heights with their respective velocities, and giving to each a weight corresponding with the number of observations made in deter- mining it, that they will be represented by a line expressing the height of the surface of the still-boxes above that of the stream by 0.000035 of the square of the velocities of the stream ; or a little more than two-tenths of one per cent of the heads which would pro- duce these velocities, and but twelve per cent of the extent of the incessant fluctuations in height of the surface of the stream.

This result proves that, with these orifices cut with care in pine planks, having their passages at right angles with the side of the trough, and having their edges so nearly in the plane of the side of

OF ARTS AND SCIENCES. 41

the trough that careful observation detected no variation therefrom, and having areas in circular form from 0.0003 sq. ft. to 0.0054 sq. ft., and one rectangular area having a height of 0.083 ft. and a length of 0.33-1 ft., there was no lowering of the piezometric column by cohe- sion of the water acting at its base ; and shows that the height of the piezometric column was in excess of that of the stream by an amount extremely small, but with large velocities it was within the practicable limits of observation.

Orifices slightly inclined. Passages normal.

Before concluding the result just obtained to be a general truth, it is important to learn in what manner it will be affected by slight modifications of the conditions under which it was obtained. These are fortunately presented, probably through unequal swelling of the wood, in the orifices on each side at Station No. 5, and at the west orifice at Station No. 9.

After the experiments were made, those with high velocities being recently completed, these orifices were found to be in the following condition : —

At Station No. 5, the orifice upon the west side being a rectangle 0.337 ft. high and 0.084 ft. wide, horizontally, had its top, bottom, and down-stream edges well in the plane of the side of the trough ; but the up-stream edge, being in this plane at the top and bottom, receded from it 0.0008 ft. at its mid height. The orifice upon the east side, being a rectangle 0.336 ft. high and 0.021 ft. wide, horizon- tally, was in the condition that the plane of the side of the trough for half a foot up stream from the orifice continued across it would cut into the down-stream side of the orifice about 0.0002 ft. back from its edge, for about two-thirds of the lower part of its height.

It is probable that these variations from a plane increased during the three months in which the experiments were made, in which case the condition presented is not applicable to the earlier experiments with small velocities.

At Station No. 9, the orifice in the west side was cut 0.168 ft. high and 0.250 ft. long, and then filled for the up stream one-third of its length by a block, leaving a square orifice. At the end of experi- ments, the edges of the original orifice were found to be in the plane of the side of the trough, and the up-stream and top edges of the block were also in this plane ; but the lower down-stream corner of the block, and consequently the lower end of the up-stream edge of the orifice, projected into the trough 0.0015 ft.

42

PROCEEDINGS OF THE AMERICAN ACADEMY

With these three orifices, the horizontal elements of the surfaces, bounded by their edges, vary from being parallel with the axis of the stream to a maximum deviation therefrom of 0° 33' in each of the ori- fices at Station No. 5, and of 0° 31' at Station No. 9.

The direction of the deviation of the surfaces being such that at Station No. 5 the particles of water in passing would impinge upon it, and at Station No. 9 they would withdraw from it.

The effect of these slight deviations is presented in the following table, and in Fig. No. 2 of Plate No. 3 : —

Station No. 5. West Side.	Station No.	5. East Side.
Mean			Mean
velocity	Mean heights of the		velocity	Mean heigh!	S of the
of	surface in still-box		of	surface ins	ill-box
water	above that at the		water	above that	at the
passing	middle of the		passing	middle of the
the	stream.		the	sti-ean	.
Station.			Station.
U	Heights.			U	Heights.
		No. of	0.0002 U1			No. of	0.00032 U2
Ft. per second.	Feet.	Obs.		Ft. per second.	Feet.	Obs.
0.63	— 0.0005	30	0.0001	0.63	— 0.0010	30	0.0001
1.05	— 0.0001	44	0.0002	1.05	_ 0 i H m I.",	44	0.0003
1.79	0.0000	66	0.0000	1.79	+ 0.0018	67	0.0010
2.88	— 0.0005	01	0.0017	2.88	+ 0.0011	61	0.0027
5.46	+ 0.0102	28	0.0060	5.46	+ 0.0109	29	0.0095
6.10	+ 0.0029	6	0.0074	6.10	+ 0.0052	6	0.0119
7.05	-f- 0.0078	12	0.0099	7.05	+ 0.0117	13	0.0159
7.97	+ 0.01- -.7	17	0.0127	7.97	+ 0.0230	18	0.0203
8.55	+ 0.0196	12	0.0150	8.55	+ 0.0292	13	0.0240
Station No. 9. If". *	t Side.
0.64	— 0.0003	51	0.00008 U*
0.0000
1.09	0.0000	52	0.0001
1.86	—0.0005	53	0.0003
3.31	— 0.0023	57	0.0009
5.79	—0.0005	2:1	0.0027
6.14	— 0 0007	23	0.0030
8.44	— 0.0067	17	0.0057
8.88	— 0.0053	8	0.0063

From these results, we see that, where the surface included by the edges of the orifice is turned, even very slightly, so that the particles of water flowing parallel with the axis of the stream strike into it, the surface of water in the piezometer stands higher than the surface

OF ARTS AND SCIENCES. 43

of the stream ; and, when turned so that the particles of water with- draw from it, the surface of the piezometer stands lower than the sur- face of the stream. Assuming that the variation is as the square of the mean velocity of the stream, the excess in height of the piezo- metric surface at the west box of Station No. 5 may be expressed approximately by heights equal to 0.0002 U'2, in which U stands for the mean velocity of the stream at the station ; and the excess in height at the east box of Station No. 5 may be expressed approxi- mately by heights equal to 0.00032 U2 ; and the depression at Station No. 9 may in like manner be expressed by 0.00008 U'2.

Orifices parallel. Passages inclined.

At Stations No. 7 and No. 10, the planes of the edges of the ori- fices were, within the limits of careful observation, either in the plane of the sides of the trough, as at Station No. 7, or parallel with this plane, and within 0.0004 ft. from it, as at Station No. 10; but at these stations the passages from the orifices, beginning at the plane of their edges, were not normal to this plane, but made therewith an acute horizontal angle.

At Station No. 7, on the west side, the angle was 45° up stream, and on the east side was 45° down stream. At Station No. 10, on the west side, the angle was 30° down stream, and on the east side was 30° up stream.

At Station No. 7, the orifices were made by boring through the sides of the trough, at the proper angle, holes 0.021 ft. in diameter ; and, though cut with great care, it was found at the end of the experi- ments that the acute edge of each was slightly ragged, but no projec- tion into the trough was perceptible.

At Station No. 10, the orifices were made with the same sized hole in plates of brass, carefully finished, and set into the sides of the trough flush ; but the swelling of the wood in the thickness of the plate, which was 0.01 ft., caused it to project 0.0003 ft. or 0.0004 ft. beyond the surface of the plates all around. The plates were 0.083 ft. high and 0.125 ft. long.

The results given in the tables for these stations are represented in Fig. No. 3, Plate No. 3.

Here we see that on the east side at Station No. 7, and on the west side at Station No. 10, in which cases the particles of water turning 45° and 30° respectively from their course would flow directly through the passage into the piezometric reservoirs, the sur- faces of the reservoirs stand higher than the surface of the stream,

44 PROCEEDINGS OF THE AMERICAN ACADEMY

and these heights may be expressed approximately at Station No. 7 by 0.0002 U\ and at Station No. 10 by 0.0005 U\

On the other hand, on the west side at Station No. 7 and east side at Station No. 10, where the passages go out up stream, the surface of the piezometric reservoir at Station No. 7 stands lower than the surface of the stream by amounts expressed approximately by 0.00025 U'\ While at Station No. 10, the surface in the reservoir is slightly above and below that of the stream, in no case more than 0.004 ft., and the mean result for all of the velocities is very nearly zero.

If there were any lowering of the piezometer by the action of cohesion at its base, it would follow that with orifices having passages so very favorable to drawing water from the reservoir, as in the two cases just considered, the lowering would be much greater than the raising above the stream in the two previous cases; but the lowering being really less than the raising tends to the conclusion that there is no lowering due to cohesion at the orifice.

The raising of the piezometric column three per cent of the head that would produce the velocity of the stream, and the lowering of one and one-half per cent of the same head by the difference in direc- tion of the passage, without any perceptible variation of the plane of the orifice from that of the side, indicate that, either from impercep- tible variations in the plane of the orifice, or from sinuosity of cur- rent, such inclined passages are not to be relied upon for accurate results.

Orifices projecting into the Stream. Passages inclined.

At Station No. 2, a hole was bored through each side of the trough, making with the inner face a horizontal angle of 48°, up stream on the west side and down stream on the east side. Into these holes were fitted brass pipes, 0.049 ft. in diameter outside, and 0.043 ft. in diameter inside, having the inner ends finished smooth with square edges. These pipes projected into the trough, so that the intersec- tion of the plane of the end of each with the plane of the side of the trough was very nearly a tangent to the outer circumference of the end.

The distance from the plane of the side to the point of the outer circumference of the end farthest removed was 0.033 ft., and to the corresponding point of the inner circumference was 0.031 ft.

At Station No. 6 were .other projections into the trough. Two brass castings were made, each consisting of a plate 0.083 ft. high,

OP ARTS AND SCIENCES. 45

0.125 ft. long, and 0.010 ft. thick, having near the middle of one side a projection of about 0.02 ft., through which was drilled, lengthwise of the plate at an angle of 30° with its face, a hole 0.02 1 ft. in diameter. The end of the hole was finished at right angles with its axis, having the circumference very nearly tangent to the surface of the plate ; and, the edge of the orifice being as thin as practicable, the outside of the projection was finished, making its elements diverge 10° from the axis of the hole, and its point farthest removed from the plane of the plate was 0.02 ft. therefrom.

When in position in the trough, the face of the plate was in the plane of the side ; and a horizontal section through the axis shows the inside of the hole, making an angle of 30°, and the outside of the pro- jection one of 20° with the side. The orifice faced down stream on the west side and up stream on the east side. During experiments, the plates did not vary more than 0.0002 ft. and 0.0003 ft. from the plane of the side of the trough.

A short time before the experiments were completed, an instrument with projections, designed to be miniature models of those at Station No. 6, was set into the west side of the trough, 0.84 ft. up stream from Station No. 6, and 0.25 ft. above the bottom.

This instrument consisted of a circular plate of brass 0.147 ft. in diameter and 0.042 ft. thick, having a hole through its centre 0.013 ft. in diameter, normal to its face, with square edges well in the plane of its face. At 0.04 ft. above and below the central hole were two others, 0.005 ft. in diameter, drilled in horizontal planes through pro- jections upon the face from opposite sides of the vertical through their centres ; the hole above the centre making an angle of 30° with the face down stream, and that below making the same angle up stream.

The orifices were finished with thin edges, in planes normal to the axes, and were very nearly tangent to the face of the instrument, from which the entire projection was 0.005 ft. The elements of the out- side surfaces were made to diverge 10° from the axes.

When in place in the trough, the face of the instrument was not more than 0.0002 ft from the plane of the side. Short brass tubes were screwed into the back of the instrument and connected with vertical glass tubes placed against a scale upon which the heights of water surfaces were read.

46

PROCEEDINGS OF THE AMERICAN ACADEMY

The results obtained at Stations No. 2 and No. 6 and with the instrument just described are given in the following table : —

Mean velocity of stream passing the orifice.	Number of obser- vations.	Height of the surface in the still-boxes above that of the middle of the stream.
At the WTest Still-box.	At the East Still-box.
U.
Ft. per sc	Feet.	Feet.
At Station No. 2.	+ 0.0030 + 0 0100 + 0.0223 + 0.0664 + 0.2469 + 0 3410	— 0.0063 U*	+ 0.0086 U2
0.64 1.03 1.74 2.70 5.23 6.25 6.39 7.39 8.18	60 148 108 119 56 34 18 19 24	— 0.0025 — 0 0063 — 0.0201 — 0.11112 — 0.1885 — 0.2719 — 0.3043 — 0.4227
— 0.0026 — 0.0067 — 0.0191 — 0 0459 — 0.1723 — 0.2401 — 0.3440 — 0.4215	+ 0.0035 + 0.0091 + 0.0260 + 0.0627 + 0.2352 + 0.3511
At Station No. 6.	+ 0.0018 + 0.0083 + 0.0259 + 0.0296 + 0.0418 + 0.0650 + 0.0722 + 0.2433 + 0.2688 + 0.3465	— 0.0033 U"	+ 0.0074 U2
0.65 1.06 1.82 1.89 2.32 2.68 301 5.63 6.08 7.11 754 8.13 8.21 8.59	180 58 102 36 36 18 131 44 30 11 42 12 84 11	— 0.0022 — 0.0044 — 0 0TJ7 — o.oni — 0.0178 — 0 0170 — 0.0326 — 0.1102 — 0 1303 — 0.1760* — 0.2141 — 0.2155 — 0.2482
— 0.0014 — 0.0037 — 0.0109 — 0.0129 — 0.0178 — 0ir_>:;7 — 0.02! t9 — 0.1046 — 0.1220 — 0.1876 — 0.2181 — 0.2224 — 0 2435	+ 0.0031 + 0.0081 + 0 0245 + 0.0264 + 0.0398 + 0.0536 + 0.0670 + 0.2346 + 0.2736 + 0.3741
At Side Instrument above Station No 6.	— 0.0025 U*	+ 0.0046 U2
7.27 7.38 8.12	33 40 138	Height of water above that of central glass tube.
In down-stream Tube.	In up-stream Tube.
Feet.	Feet.
— 0.1294 — 0.1334 — 0.1635	+ 0.2370 + 0.2369 + 0.3109
— 0.1321 — 0.1361 — 0.1646	+ 0.2429 + 0.2505 + 0.3033
* Air drew into West tube at times.

OF ARTS AND SCIENCES. 47

These results are also represented graphically upon Plate No. 4, where it will be seen they may be expressed with a good degree of approximation in terms of the mean velocity of the stream, as follows : —

At Station No. 2.

West side — 0.0063 U2

East side + 0.0086 U2

At Station No. 6.

West side — 0.0033 U2

East side + 0.0074 U2

At Side Instrument near Station No. 6. Down-stream Tube .... — 0.0025 U2 Up-stream Tube + 0.0046 U2

In these results, we see that with the orifice inclined down stream the lowering of the reservoir below the surface of the stream is less in amount than the raising of the reservoir above the surface of the stream where the orifice is inclined up stream at the same angle ; the former being in the three cases seventy-three, forty-four, and fifty- four per cent of the latter.

Orifices parallel. Passages normal. Tubes projecting.

At Station No. 3, holes were bored at right angles with the plane of the side, and into these were fitted iron pipes. On the west side, the pipe being 0.0G8 ft. in diameter outside, and 0.052 ft. in diameter inside, had a well finished end parallel with the plane of the side, with square edges. On the east side, the pipe was 0.109 ft. in diameter outside and 0.08G ft. in diameter inside, with end designed to be finished like that upon the west side ; but it was not done with care, and the up-stream edge was, at the close of the experiments, found to project 0.0009 ft. farther into the stream than the down-stream edge, and the top edge to project 0.0003 ft. more than the bottom edge.

At first, both pipes were kept flush with, or without any projection beyond the plane of the side, and afterward were pushed out into the stream, as indicated in the table giving a summary of results at this station.

With velocities from 0.64 ft. to 2.77 ft. per sec, the westerly pipe being flush with the side, the average height in the reservoir is the same as that at the middle of the stream, within the practicable limits of measurement.

The same result obtains upon the east side up to velocities exceed-

4» PROCEEDINGS OF THE AMERICAN ACADEMY

ing 6 ft. per sec. "With velocities between seven and' one half feet and eight and one half feet per sec, the average height in the reservoir was greater than that at the middle of the stream by 0.0108 ft.

But, immediately upon projecting one of the pipes into the stream, a marked change is observed : the surface in the reservoir is imme- diately lowered ; with a velocity of 2.77 ft. per sec, the westerly pipe being flush with the side, the surface in the reservoir was 0.0011 ft. higher than that in the stream, but, upon projecting this pipe 0.013 ft. into the stream, the surface in the reservoir immediately lowered to 0.0259 ft. below that of the stream; the mean velocity continuing 2.80 ft. per sec. With the same projection of 0.013 ft., with veloci- ties from 2.09 ft. to 8.35 ft. per sec, the lowering of the surface of the reservoir below that of the stream increased from 0.0187 ft. to 0.2196 ft. in a series expressed approximately by heights equal to 0.0033 U% as shown in Fig. No. 4, Plate No. 3.

Increasing the jirojection to 0.055 ft., the mean velocity being 7.95 ft. per sec, the lowering of the reservoir was 0.4392 ft., or 0.00G9 U'1 ; and it would probably have been more, but at this height the surface of the reservoir was drawn below the top of the pipe, even to its centre, and air was drawn into the stream.

The form of the stream of air at the orifice revealed to the eye the cause of the lowering in the reservoir. It was evident that the par- ticles of water striking the up-stream side of the pipe were deviated in part nearly at a right angle toward the middle of the stream, and their course again bent down stream, forming a path approximating a quadrant of an ellipse whose conjugate axis lay in the end of the pipe parallel with the axis of the stream.

Upon withdrawing the pipe and reducing the projection to 0.007 ft., the lowering in the reservoir is expressed by 0.0011 W1.

At the east side, with the pipe so placed that its most projecting point was in the plane of the side of the trough, and with a mean velocity of stream of 7.95 ft. per sec, the surface of water in the reservoir was 0.0009 ft. above that of the stream ; but, upon projecting the pipe 0.008 ft., the surface in the reservoir was lowered to 0.1080 ft. below that of the stream, the mean velocity continuing 7.98 ft. per sec. This lowering may be expressed by 0.0017 U2.

Upon projecting this pipe 0.012 ft., the lowering, with a mean velocity of 7.86 ft. per sec, amounted to 0.1797 ft., or 0.0029 XJ-.

If we knew the actual distribution of velocities throughout the stream, it would be interesting to trace the relation of the lowering of the reservoir and the velocity of the stream just at the end of the pipe.

OF ARTS AND SCIENCES.

49

With our present knowledge, this cannot be done with accuracy ; but from observations, which I will not describe, I am able to present an approximate result which will serve to illustrate one principle.

Taking, for example, the conditions when the mean velocity of the stream is 8 ft. per sec, I construct the following table : —

Distance from side of trough.	Approxi- mate velocity at the distance given.	Head that would pro- duce this approxi- mate velocity.	Lowering of reservoir below surface of stream.	Lowering of reservoir divided by head producing approximate velocity.	Velocity due lowering.	Velocity due lowering divided by approximate velocity.
Feet.	Ft. per sec.	Feet.	Feet.	Ft. per sec.
0.007 0.008 0.012 0.013 0.055	5.6 5.8 6.2 6.3 8.0	0.488 0.523 0.598 0.617 0.995	0.070 0.109 0.186 0.211 0.442	0.14 0.21 0.31 0.34 0.44	2.12 2.65 3.46 3.68 5.33	0.38 0.46 0.56 0.58 0.67

Recurring to the observations when the westerly tube projected 0.055 ft. and the paths of some of the particles were found to deviate about ninety degrees, and, passing through a quadrant of an ellipse, again resume a direction parallel with their former course, it would be reasonable to conclude that, with a projection of a few thousandths of a foot, the deviation of the paths would be less than ninety degrees, and the curve would be flattened, and become more like a segment taken nearer the transverse axis. In this case, the lowering of the reservoir would not bear a constant relation to the head which would produce the velocity existing at the end of the pipe, but would be a fraction of this head, increasing with the distance from the side, rapidly at first, and then slower, until reaching a limit would remain constant. This conclusion is confirmed by the results of the table, in which with distances from 0.007 ft. to 0.055 ft., the velocity due a height equal to the lowering of the reservoir increases from 0.38 to 0.67 of the veloc- ity at the end of the pipe, and this increase is in a rapidly decreasing series.

I have reason to conclude, from experiments made elsewhere, that the lowering of the reservoir depends also upon the thickness of the end of the pipe ; for I found by projecting a pipe 0.02 ft. in diameter, having very little thickness at the end, into water flowing in an iron pipe one foot in diameter, with a mean velocity of 9 ft. per sec, a lowering of the piezometric column greater than that above given ; namely, for the same distances from the side, the velocity due a height equal to the lowering was from seventy to ninety one-hundredths vol. xiv. (n. 8. VI.) 4

50 PROCEEDINGS OF THE AMERICAN ACADEMY

of the velocity with which the water approached the end of the pipe, and at greater distances the velocity due the lowering increased until it exceeded the velocity of the approaching water.

Conclusions.

From the 6000 and more observations made at this trough upon the various forms and kinds of orifices, I reach the following general conclusions : —

The first group of experiments shows that with orifices whose edges are in the plane of the side of the conduit, with passages normal to this plane, the surface of water in the piezometers does not stand below the surface of the stream.

On the contrary, the general results at the orifices of this kind indicate, for the higher velocities, an excess of height in the piezometer expressed by 0.000035 U\

This is but twelve per cent of the incessant fluctuation of the sur- face ; but, though a very small quantity, it is, with the higher velocities experimented upon, a measurable one, and its cause is to be sought.

Experiments at Station No. 6 and those with the instrument having projections of 0.005 ft. show that the height above the surface of the stream to which water in the piezometer is forced is greater when the orifice is turned toward the current than the height below the surface to which it is drawn when the orifice is turned so that the stream draws away from it ; in these cases nearly twice as great, the angle with the plane of the side and the amount of projection being the same when facing with or against the current. The obser- vations at Station No. 5 and on the west side at Station No. 9 give a similar result.

The edges of the orifices of the first group of experiments which were, within the limits of careful observation, in the plane of the side of the trough, were of course not perfectly in this plane ; the proba- bilities are that they deviated as much from this plane upon the down-stream side as upon the up-stream side, in which case it follows from the experiments just cited that the effect of these imperfections would give an average height of the piezometers greater than the height of the stream. If the comparative value of the excess of and diminution in height of the experiments cited be applied to these results, the average height of piezometers for velocities above 5 ft. per sec. will be reduced to the average height of the stream, within the practicable limits of measurement. This result indicates, with a nearness of approximation unusual in hydraulic investigations, that

OP ARTS AND SCIENCES. 51

with the plane of the orifice accurately in the plane of the side of the conduit the piezometer will indicate the true height of the surface of the stream.

The second group of experiments shows that, with extremely slight variations of the plane of the orifice from the plane of the side, the piezometer indicates a greater height or a less height than the surface of the stream, according as these variations cause the stream to strike into or draw away from the plane of the orifice ; and, in connection with the experiments at Station No. 6 and elsewhere upon definitely formed projections, they lead quite definitely to the conclusion that with an orifice whose edges are in the plane of the side, and passage normal thereto, the piezometric column will stand neither above nor below the surface of the stream, but will indicate the true height of this surface.

The third group of experiments in which the plane of the orifice was in, or nearly in, the plane of the side, but the passage from it turned sharply up stream or sharply down stream, shows that, with such ar- rangement, variations from the plane of the side which would escape careful observation, or slight inclinations of the current, may lead to variations of considerable magnitude in height of the piezometric column above or below that of the surface of the stream, consequently such arrangements are not to be relied upon.

The fourth group of experiments in which the orifice projects into the stream, and the plane of its edges makes a large horizontal angle with the plane of the side, either up stream or down stream, shows that with the same angle and the same projection into the stream the piezometric column connected with the orifice facing up stream stands above the surface of the stream by a much greater amount than the piezometric column connected with the orifice facing down stream stands below the same surface ; the latter height being, in the examples before us, from forty-four to seventy-three per cent of the former.

The fifth group of experiments in which pipes at right angles with the current project into the stream, the end of the pipe having square edges, shows that with such an arrangement the piezometric column stands lower than the surface of the stream.

This follows from the fact made evident that the particles of water which woidd pass where the pipe is are deviated from their course, a part of them moving lengthwise of the pipe, and, being projected in a curve around its end, cause the pressure into the end of the pipe to be diminished below that of the normal pressure upon the sides of the

52 PROCEEDINGS OP THE AMERICAN ACADEMY

trough, by an amount which is a varying fraction of the pressure which would produce the velocity with which the water approaches the pipe.

This fraction increases with the projection from the side, from zero to forty -four one-hundredths, in the experiments in this trough ; and in the experiments alluded to in a closed conduit uuder pressure, with a smaller pipe having a thin end, it increased more rapidly with the same distances from the side, and with greater distances increased until the lowering exceeded the height which would produce the velocity of the approaching water.

The lowering of the piezometric column under circumstances like these just presented confirmed Dubuat* in his conclusion that water in motion pressed upon the sides of a conduit with a pressure less than that due its depth, by the whole amount of pressure that would produce its mean velocity, which conclusion Navier f controverted, but which has been presented in works upon hydraulics quite gener- ally until the publication of the results of M. Darcy, which in general confirmed the position of Navier, but left in doubt the indications of the piezometer ; but the experiments now presented show that with currents flowing parallel with the side of a straight conduit, with orifices having edges in the plane of the side and with passages normal thereto, there is no lowering of the piezometric column, but that it indicates the true height of the surface of the water in the conduit when in motion, as well as when at rest. And we have a reliable datum plane, to which observations in hydraulics may be referred.

Note. Upon the Limits of Accuracy that may be obtained with Piezometers.

The experiments of the first group were united, because from careful observation, made before any results were computed, the planes of the orifices were regarded as satisfactorily in the plane of the side. No deviation therefrom was perceptible in the light in which they could be seen that enabled me to say they inclined one way or the other. This light was good upon the side of the straight edge presented to the eye ; but, looking down into the trough, no light could be seen be- yond, and very slight variations could not be detected there, which could be seen if the bearing surfaces were between the eye and the light.

* Principes d'Hydraulique. Par M. Dubuat. Paris, 1816. Art. 439 and 453. t Architecture Hydraulique. Par Belidor. Paris, 1819. Page 342.

OF ARTS AND SCIENCES. 53

It may be that variations of 0.0002 ft. were overlooked, though such were detected at Station No. 5.

To obtain as definite an idea as we may of the precision necessary to obtain accurate results with a piezometer, let the results obtained at the several orifices of the first group be worked up separately. The heights of the piezometers above and below the surface of the stream will be expressed approximately as follows : —

Station No. 4. West side, — 0.00004 U2 East side, — 0.00006 U2 Station No. 8. West side, -t- 0.00022 U2 East side, + 0.00006 U2 , Station No. 9. East side, •+- 0.00002 U2

Applying as well as we may the results obtained in the second group of experiments, and assuming the variation in height to be propor- tional to the angle of inclination with the plane of the side, of the horizontal elements of the surface bounded by the edge of the orifice, it will be seen that an extreme variation from the plane of the side in the length of any of the longer of these elements of 0.0004 ft., 0.0002 ft., 0.0003 ft., 0.0002 ft., and 0.0002 ft., respectively at the several orifices, in the order in which they have been named, will account for the several variations in the height of the piezometric columns above or below the surface of the stream ; and a less varia- tion from the plane of the side, in the length of any of the shorter horizontal elements of the circular orifices, would serve to account for them.

It will be observed that the heights by the piezometer whose orifice was 0.334 ft. long horizontally indicated more nearly than those with smaller orifices the actual height of the stream.

From these results, it is evident that it is entirely within the practicable limits of construction to make piezometers that will indi- cate the true height of the stream, within the practicable limits of observation.

54 PROCEEDINGS OF THE AMERICAN ACADEMY

III.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF HARVARD COLLEGE.

RESEARCHES ON THE SUBSTITUTED BENZYL COM- POUNDS.

By C. Loring Jackson and Alfred W. Field.

FOURTH PAPER.

PARACHLORBENZYL COMPOUNDS.

Presented December 12th, 1877.

Parachlorbenzylchloride, C(iJIiClCJI2CL In beginning these re- searches, we had no idea that it would be necessary to investigate this substance, as, since its discovery by Beilstein and Geitner,* it had been prepared and studied by a great number of chemists, and had served as the starting-point for the preparation of all the parachlorbenzyl compounds known. But, on looking into the subject more carefully, we found that it had been made invariably from the product of the chloriring of toluol in the cold, which Hubner and Majertf have proved, by their work on the sulpho-acids, is a mixture of ortho and parachlortoluol ; while, more recently, Oscar Emmerling $ has shown that the product from oxidizing it with potassic permanganate contains more ortho than parachlorbenzoic acid. The parachlorbenzylchloride of previous chemists, therefore, must have been contaminated with a larger or smaller amount of the ortho compound, which escaped detec- tion, because the method used by them to test the purity of their preparations consisted in oxidizing with potassic dichromate and sul- phuric acid, and, as this destroys the ortho modification completely, a pure parachlorbenzoic acid was the only product. This oversight is not surprising when it is borne in mind that the more important of

* Beilstein and Geitner, Zeitschr. der Chem., 1866, p. 307 ; also p. 17. t Hubner and Majert, Ber. D. Ch. G. vi. p. 790. J 0. Emmerling, Ber. D. Ch. G. viii. p. 880.

OF ARTS AND SCIENCES. 55

these papers appeared in 1866, when the nature of aromatic isomeres was very imperfectly understood.

For the reason given above, we determined to prepare the para- chlorbenzylchloride from perfectly pure parachlortoluol, and hoped that it might be a solid, instead of the oily liquid described by our predecessors ; indeed, it seemed hard to believe that it could be a liquid, as the parachlortoluol melts at 6£° (Hiibner and Majert), and we had already found that the introduction of bromine into the side- chain raised the melting-point to 48 1°.

Preparation. Parachlortoluol was made from pure paratoluidine by treatment with hydrochloric acid and potassic nitrite, according to a modification of the method of Hiibner and Majert, * described in connection with parachlorbenzylbromide in the first paper f of this series. The 31 grs. that we obtained distilled over completely be- tween 160° and 161°, and froze between 4° and 5° in white plates looking exactly like parabromtoluol, which melted from 7° to 7|-°. These results agree essentially with those of Hiibner and Majert,* who found the boiling-point 160|°, the freezing-point a little above 0°, and the melting-point 6|-°. To convert this into parachlorbenzyl- chloride, a stream of chlorine was passed into it while it stood in a paraffine-bath heated to 166°: when the increase in weight showed that somewhat more than the calculated amount of chlorine had been taken up (the 27 grs. of parachlortoluol used had become 35 grs. instead of 34.3 grs.), the chlorine was stopped, and the product put in a freezing mixture of ice and salt, where it partially solidified in white needles, which were drained on the filter-pump, and recrystal- lized from alcohol. The yield was very small, and all attempts to get more from the mother-liquors were fruitless. The following analyses of the substance dried in vacuo show that it is the expected parachlorbenzylchloride.

0.6760 gr. of substance gave 1.2930 gr. of C02 and 0.2458 gr. of H204

0.2755 of substance gave, by Klobukowski's § modification of Emil Kopp's method, 0.4946 gr. AgCl.

* Hiibner and Majert, Ber. D. Ch. G. vi. p. 794.

t These Proceedings, XII. (n. s. IV.) p. 218.

\ Combustion of these parachlorbenzyl compounds with plumbic chromate alone was found to yield good results much more easily than the more usual method of combustion in a stream of oxygen, and therefore was used in the analysis of all these substances.

§ Klobukowski, Ber. Dt. C. G. 10, p. 290.

56 PROCEEDINGS OF THE AMERICAN ACADEMY

	Calculated for C7H6C12.	Found.
Carbon	52.17	52.17
Hydrogen	3.73	4.04
Chlorine	44.10	44.41

100.00 100.62

Properties. White lustrous prisms or needles, often more than 3 cm. long, with an agreeable aromatic odor and most violent action on the mucous membrane and tenderer parts of the skin ; nielting-point, 29° ; so volatile that a crystal exposed to the air disappears in a few hours ; sublimes even at ordinary temperatures in needles ; it is very little, if at all, soluble in water, but readily in warm, less so in cold, alcohol, very easily in ether, benzole, carbonic disulphide, and glacial acetic acid. That it is a chlorbenzyl compound was proved by boiling it for some time with water, in a flask with a return-cooler, when the parachlorbenzylalcohol and hydrochloric acid were formed. Boiled with a solution of potassic permanganate, it was easily oxidized, giving an acid which melts between 233° and 235° (O. Emmerling gives 234° as the melting-point of parachlorbenzoic acid) ; this acid boiled with water, in which the orthochlorbenzoic acid is much more soluble than the para, gave a solution which deposited crystals melting also at 233°-235°: as potassic permanganate oxidizes instead of destroying the ortho compounds, this proves that our parachlorbenzylchloride is perfectly free from isomeric impurities.

Having thus proved that the parachlorbenzylchloride used as a starting-point for the preparation of derivatives by Beilstein, Kuhl- berg, Neuhof, and others, really did contain the ortho compound, as we had previously inferred, we next proceeded to make some of these derivatives, and redetermine their properties. In this work, the more easily purified parachlorbenzylbromide was used instead of the chloride.

Parachlorbenzylalcohol, G^H^CIGH^OH, was made by boiling the bromide (or chloride) with water in a flask with a return-cooler. The formation of hydrobromic (or hydrochloric) acid by this reaction was proved by testing the water, which had become acid, with argentic oxide, when argentic bromide (or chloride) was formed, and the acid reaction disappeared. The alcohol was made also from the acetate by boiling with water : sealing with aqueous ammonia, as recom- mended by Beilstein and Kuhlberg, being found in this case un- necessary : it was purified by crystallization from boiling water, dried in vacuo, and analyzed.

OF ARTS AND SCIENCES. 57

0.4517 gr. of substance gave 0.9754 gr. C02 and 0.2175 gr. H20. Calculated for C7H6C10H. Found.

Carbon 58.94 58.89

Hydrogen 4.91 5.34

Properties. Beautiful pointed white ribbons usually one or two inches long, with a brilliant pearly lustre and characteristic smell, but no action on the mucous membrane or tenderer parts of the skin ; melting-point, 70 £° ; sublimes very easily in white needles, and can be purified in this way ; evaporates slowly on exposure to the air, and distils in a current of steam ; slightly soluble in cold, much more so in hot water, very easily in alcohol, ether, benzole, carbonic disulphide, and glacial acetic acid. It is oxidized by a mixture of potassic dichro- mate and dilute sulphuric acid, giving parachlorbenzoic acid ; melting- point, 233° (234° O. Emmerling).

The chlorbenzylalcohol obtained by Beilstein and Kuhlberg * differs from the above only in melting at 66°.

Parachlorbenzylcyanide. The product of the reaction of alcoholic parachlorbenzylbromide and potassic cyanide, when precipitated by water, was a yellow oil, which showed no signs of solidifying in a mixture of ice and salt : after standing in an open watch-glass for three or more weeks, however, it did deposit crystals when put in a freezing-mixture, but in such small quantity that it was impossible to purify them thoroughly ; and it did not seem worth while to spend the large amount of time and material necessary to get enough of them for complete study. The crystals, after sucking out the oil with filter-paper, proved to be good-sized colorless prisms ; and, as one specimen of a twinned form like a quatrefoil was observed, there can be no doubt that the substance is analogous to the parabrombenzyl- cyanide : f its melting point is 29° ; and it is easily soluble in alcohol and ether, being left on evaporation of the solvent as an oil which crystallizes when stirred.

The yellow oil from which the crystals were obtained has also the nitrile smell, and is converted, by heating to 100° in a sealed tube with hydrochloric acid, into parachloralphatoluylic acid : it must there- fore be either the same substance as the crystals, prevented from solidifying by a small quantity of impurity, or the crystals may be a polymeric form of the oil. The cyanide was mentioned by Neuhof %

* Beilstein and Kuhlberg, Ann. Chem. Pharm. 147, p. 339. t These Proceedings, XII. (n. s. IV.) p. 222. t Neuhof, Ann. Chem. Pharm. 147, p. 347.

58 PROCEEDINGS OF THE AMERICAN ACADEMY

as a dark oil, made by heating chlorbenzylchloride to 120°-130° in a sealed tube with potassic cyanide and alcohol ; but no attempt was made to purify or analyze it. This heating in a sealed tube to 120°— 130° is, as seen from the above, unnecessary.

Parachloralphatoluylic Acid, C6JIiClCIf9COOIT, made by heating the nitrile to 100° in a sealed tube with fuming hydrochloric acid, or by boiling it with dilute sulphuric acid in a flask with a return-cooler, was purified by solution in ammonic hydrate, precipitation with sul- phuric acid, and recrystallizing from boiling water. Its composition was established by an analysis of the silver salt.

Properties. White needles, often two centimetres long, sometimes thick and pointed, with a pleasant smell ; melting-point, 103^°-104° ; sublimes easily in little plates, and can be distilled, although not quickly, in a current of steam ; somewhat soluble in cold, much more so in hot water, freely in alcohol, ether, benzole, carbonic disulphide, and glacial acetic acid. Aqueous ammonia dissolves it readily, but the ammonic salt is decomposed, at least in part, by evaporation the acid being set free.

A chloralphatoluylic acid has been already described as the para compound by Neuhof,* who made it, however, from chlorbenzylchloride; the melting-point was 60°, and it separated from its salts as an oil which soon solidified, otherwise it resembled our acid, except that it seems to have been much more soluble in water. Later, Radziszew- ski f made a similar acid, melting at 68° by chloriring alphatoluylic acid.

Argentic Parachloralphatoluylate, C^H^WH.^COOAg, fell as a white, curdy precipitate, upon adding argentic nitrate to a neutral solution of the ammonic salt of the acid. It was washed with water, dried at 100°, and analyzed.

0.3410 gr. of substance gave, precipitated from a nitric acid solution, with hydrochloric acid, 0.1788 gr. of AgCl.

Calculated for C8H6C102Ag. Found.

Silver 38.91 39.44

Properties. A white, curdy mass, consisting of clumps of silky microscopic needles, which blackens rapidly in direct sunlight, but only very slowly in diffused daylight ; very slightly soluble in boil- ing water, almost insoluble in cold, freely soluble in dilute nitric acid and ammonic hydrate.

* Neuhof, Ann. Chem. Pharm. 147, p. 347. t Radziszewski, Ber. D. Ch. G. ii. p. 207.

OF ARTS AND SCIENCES. 59

Neuhof obtained a similar salt, but describes it as more soluble in water than ours.

We did not succeed in getting a pure, well-defined calcic salt, al- though we tried to do so several times. By adding lime-water to the acid till the reaction was alkaline, removing the excess of lime by carbonic dioxide, and allowing the solution to evaporate spontaneously, arborescent groups of white needles were obtained. These lost 9.84 per cent when dried at 100° ; 2 molecules of crystal water would give 8.68 per cent; 2\ molecules, 10.61 per cent; the loss, there- fore, does not correspond to any probable amount of water of crys- tallization, and it seemed likely that something beside water was given off, as there was a slight sublimate on the upper watch-glass, and the substance had become somewhat brown, with a semifused look very unlike its original appearance. It, however, contained 10.36 per cent of calcium, and may therefore have been the anhydrous salt which needs 10.55 per cent. Other experiments under different conditions gave no better results, and we therefore decided that the salt was not important enough to repay a thorough study, which would use up a great deal of time.

The baric salt was even less well defined than the calcic: it was prepared in the same way, and appeared on evaporation of its solution over sulphuric acid as a colorless varnish, part of which changed on stirring into a radiated crystalline mass. This became white and opaque when treated with cold water, and when boiled with water gave an acid reaction and the smell of the acid. If the solution was evaporated on the water-bath instead of over sulphuric acid, a sticky gum was left. Neuhof's baric salt was similar to ours, and gave him an amount of barium corresponding to an acid salt. His calcic salt, on the other hand, contained one molecule of water, which it lost at 100°.

A solution of the acid in ammonic hydrate, from which the excess of ammonia has been driven off on the water-bath, gives reactions with salts of the various metals similar to those of the corresponding brom-acid.* The bluish-green flocks with cupric sulphate, yellowish- brown with ferric chloride, and white with plumbic acetate or mercurous nitrate are especially characteristic.

Parachlorbenzylsulphocyanate, OeHi CI GHt SCN, made by boiling the bromide with an alcoholic solution of potassic sulphocyanate, was purified by freezing with snow and salt, sucking out the oil with filter-

* These Proceedings, XII. (n. s. IV.) p. 225.

60

PROCEEDINGS OP THE AMERICAN ACADEMY

paper, and recrystallization from alcohol with the help of a freezing- mixture. It was dried in vacuo and analyzed. 0.1569 grs. substance gave 0.1985 grs. BaS04.

Calculated for C^CISCN. Found.

Sulphur 17.43 17.38

Properties. White, flattened needles, often over an inch long, with a strong, disagreeable smell; melting-point, 17°; does not distil with steam, but seems to be slowly decomposed by it, a few brown drops with a smell like that of benzaldehyd passing over ; mixes with alco- hol, ether, benzole, carbonic disulphide, and glacial acetic acid, but not with water.

This substance has not been made heretofore : it resembles the cor- responding bromine compound very closely in every thing but melting- point.

Parachlorbenztlamines.

These substances have been studied already by Berlin, * who pre- pared them by heating the chlorbenzylchloride with alcoholic ammonia for one week in the steam-bath. The product was worked up by a needlessly complex process, consisting, when stripped of its unneces- sary steps, in separating one portion of the bases by conversion into their chlorides and crystallizing from alcohol, while in the remainder the tertiary amine was destroyed by distillation with bromine and water, and the bromides of the remaining amines separated by crys- tallization. The properties of the tertiary and primary amines, as described by him, are in no way peculiar ; but he obtained four iso- meric forms of the secondary amine, which were themselves undis- tinguishable yellow oils, but differed in the melting-points of their salts, as shown in the following table : —

Name of Salt.	Melting Points.
a	P	7	d
Chloride .... Bromide .... Iodide .... Nitrate ....	288°-289° 283°-290°	225°-228° 224° 215° 204°-205°	218°-220° 210°-212° 187° 193°	221°-222° 198°-199° 216°-218° 177°-179°

These salts also differed in solubility, the a modification being the least, the 5 the most soluble : they were separated by crystallization

* Berlin, Ann. Chem. Pharm. 151, p. 137.

OP ARTS AND SCIENCES. 61

of the bromides from water. These observations rendered a repetition of Berlin's work very interesting ; but we did not follow the process given by him, as we have found a much more easy and simple method for the separation of the bases. Alcoholic ammonia acted very quickly, even in the cold, on parachlorbenzylbromide : the product from this or from the action in a sealed tube at 100° consisted of crystals either of the bromide of the tertiary amine or of the base itself, and of an alcoholic solution, which, filtered off and evaporated on the steam- bath, yielded the bromides of ammonium and of the primary and secondary amines with some free tertiary amine. This residue, after washing with water to remove the bromides of ammonium and the primary amine, was repeatedly crystallized from hot alcohol, until it was divided into slightly soluble scales of secondary bromide and needles of the free tertiary amine readily soluble in boiling alcohol.

Triparachlorbenzylamine, (C6JIiClCIl2)3]!i, was freed from a trace of bromide by crystallizing from ether, dried in vacuo, and analyzed.

0.7096 grs. of substance gave 1.6780 grs. C02, and 0.3300 grs.

H20.

Calculated for (CjHgCl^N. Found.

Carbon 64.78 64.49

Hydrogen 4.61 5.16

Properties. Bunches of white needles, when crystallized from al- cohol ; from ether it separates as an oil, which solidifies after some time in flattened prisms ; it is also deposited from the action of cold alcoholic ammonia on parachlorbenzylbromide in short, thick, well- formed crystals, with rhombic faces ; melting-point, 78^° ; insoluble in water, very slightly soluble in cold, freely in hot alcohol, and in ether, benzole, and carbonic disulphide, less so in glacial acetic acid.

The chloride was obtained in an impure state when an alcoholic solution of the base was heated with strong hydrochloric acid ; after standing 24 hours, the solution was allowed to evaporate spontaneously, when balls of radiated needles were left which melted at about 196°, were soluble in alcohol, ether, and glacial acetic acid, slightly in water, and insoluble, or nearly so, in carbonic disulphide and benzole ; the alcoholic solution left a viscous mass, which changed into needles slowly. After drying in vacuo, it lost, in the steam-bath, an amount equal to less than one molecule of water ; but its melting-point was unaltered, and, as it yielded crystals of the free amine on repeated treatment with alcohol, it does not follow that the loss was nothing but water. We could find no satisfactory method of purifying this, or of making a purer substance. The bromide obtained in the prepa-

62 PROCEEDINGS OF THE AMERICAN ACADEMY

ration of the amines crystallizes in scales like those of the bromide of the secondary amine soon to be described, but less soluble in alcohol.

Triparachlorbenzylamine Chlorplatinate, \_(C6Hi ClCff.7)3NH].,Pt Cl6, was made by adding aqueous platinic chloride to an ethereal solution of the base, and washing with water, alcohol, and ether ; dried at 100°, it gave the following results on analysis : —

I. 0.2380 grs. substance gave 0.0405 grs. platinum.

II. 0.2796 grs. substance gave 0.0471 grs. platinum.

Found. Calculated for [(C7H6Cl)3NH]2PtCl6. I. H.

Platinum 16.54 17.01 16.84

Properties. Pale orange microscopic irregular plates, almost insol- uble in water, alcohol, and ether.

It is worthy of especial note that Berlin's tertiary chlorbenzylamine melted at 88°-89°, as this is the only case in which we have found the melting-point of the pure substance lower than that of the impure. His chloride melting-point, 170°-175°, crystallized in well-formed rhombohedra with two molecules of water, which it lost in vacuo. Our (impure) salt differed from his not only in appearance and melt- ing-point, but also in losing nothing in vacuo ; and we have never observed any rhombohedra like those described by him, although we have tried very often and under various conditions to obtain them.

Diparachlorbenzylamine, {C^H^WH^^NH. The bromide of this base, separated from the other amines as described above, and purified by repeated boiling with alcohol, was decomposed with aqueous sodic hydrate ; the oil thus obtained solidified on stirring, especially if it was touched with a crystal of the substance.

Properties. White radiating bladed crystals ; melting-point, 29° ; insoluble in water, soluble in alcohol and glacial acetic acid, freely soluble in ether, benzole, and carbonic disulphide.

The chloride fell as a white precipitate on adding hydrochloric acid to an alcoholic solution of the base ; microscopic rhombic and pris- matic plates apparently monoclinic, slightly soluble in water, alcohol, and glacial acetic acid, insoluble in ether and carbonic disulphide ; melting-point, 288°.

Diparachlorbenzylamine Chlorplatinate, [( C6IIi ClCH.^^NH^Pt Cl6, made by adding aqueous platinic chloride to the alcoholic solution of the base, and purified by washing with water, was dried at 100°, and analyzed.

0.2389 grs. substance gave 0.0496 grs. platinum.

OP ARTS AND SCIENCES. 63

Calculated for [(C7H6Cl)2NH2].2PtCl6. Found.

Platinum 20.90 20.76

Properties. Pale yellow scales (deeper in color than the corre- sponding salt of the tertiary amine), slightly soluble in boiling water, almost insoluble in cold water and alcohol.

The bromide of the base was obtained during the preparation of the amines in white scales very slightly soluble in water or alcohol, insoluble in ether, easily decomposed by aqueous sodic hydrate, and melting with decomposition between 280° and 290°.

The salts just described are identical with those of the a modifica- tion of Berlin's secondary chlorbenzylamine ; and, as we could find no trace of any other modifications, there can be but little doubt that the /3, }', and 8 forms of Berlin consisted of mixtures of para- and ortho- compounds, in varying proportions, and this view is still further sup- ported by the fact that the melting-points of these so-called isomeres are very near together, those of the chlorides in fact all lying within ten degrees.

Monoparachlorbenzylamine, G^H^GIGH^NH^ precipitated from the aqueous solution of its bromide with sodic hydrate and distilled with steam forms a colorless oil nearly, if not completely, insoluble in water, but soluble in ether ; on exposure to the air it is converted, almost at once, into a white soluble crystalline carbonate ; if therefore care is not taken to exclude carbonic anhydride, small quantities of the amine seem to dissolve easily in water.

The carbonate was made by exposing the free base to carbonic anhydride or even to the air, and was always left when an ether extract containing the base was allowed to evaporate spontaneously. Crystallized from water, it forms white plates often of considerable size, from alcohol needles; melting-point, 114°-115°; it dissolves slowly in cold, quickly and freely in hot water and alcohol ; sodic hydrate sets free the oily amine.

The chloride made by dissolving the carbonate in hydrochloric acid crystallizes in long, narrow white plates, soluble in water and alcohol, sparingly soluble in glacial acetic acid, and essentially insoluble in ether, benzole, and carbonic disulphide; melting-point, 239°-241°.

Monoparachlorbenzylamine Ghlorplatinate, ( G^HJJlGH^NH^^tGl^ made by mixing a solution of the chloride of the base with platinic chloride, purified by washing with a mixture of alcohol and ether, and dried at 100°, gave the following result: —

0.3067 grs. substance gave 0.0866 grs. platinum.

64

PROCEEDINGS OP THE AMERICAN ACADEMY

Platinum

Calculated for (C7H6ClNH8)2PtCl6. Pound. 28.39 28.23

Properties. Bright yellow branching plates or needles, arranged in round woolly groups when crystallized from water, in which and alco- hol it is decidedly soluble.

The bromide of the base formed in the preparation of the amines resembles the chloride in appearance and solubility, but is somewhat less soluble in cold water, and melts with decomposition between 225° and 230°.

The foregoing results differ from those obtained by Berlin only in the melting-point of the chloride, which he found 197°; he gives no melting-points for the carbonate and bromide.

To make it easier to compare the new melting-points with those in use heretofore, we have collected them in the following table ; the second column of which gives the melting-points of the pure sub- stances made by us, and the third the melting-points determined by the chemists mentioned in the fourth column.

Name of Substance.

True Melting-point

Old

Melting-point

Authority for Old Melting-point.

Parachlorbenzylchloride . . Parachlorbenzylbromide . . Paracblorbenzylalcohol . . Parachlorbenzylcyanide . . Paraehloralphatoiuylic Acid

Parachlorbenzylsulphocyanate Primary Amine ....

,, „ Chloride .

,, ,, Bromide .

„ ,, Carbonate

Secondary Amine. . . .

„ „ Chloride

„ ,, Bromide

Tertiary Amine ....

,, ,, Chloride .

29° 48J° 70J° 29J ( ?) 103i-104o

17°

Liquid.

239°-241°

225°-230°

114°-1150

29°

288°

1>(I -."Ml-1

78*° 196° (?)

Liquid.

66°

Liquid.

60°

68°

Liquid. 197°

Liquid. 288D-289° 283°-290°

KK Kit

170°-175°

Beilstein and Geitner.

Beilstein and Kuhlberg.

Neubof.

Nenhof.

Radziszewski.

Berlin.

Berlin.

The revision of the parachlorbenzyl compounds will be continued in this laboratory ; in fact, the aldehyde and some of the sulpho- derivatives have been already made and partially studied by Mr. J. Fleming "White, whose work will form the subject of a later paper of this series.

OF ARTS AND SCIENCES. 65

IV.

THE DEVELOPMENT OF LEPIDOSTEUS. By Alexander Agassiz.

Presented Oct. 8, 1878.

PART I.

It has been my good fortune this spring to succeed in hatching Lepidosteus from the egg, and in raising the young until they showed externally, at least, the principal structural features of the adult.

Like many other American naturalists, I had for many years been on the lookout for the breeding-places of our Lepidosteus and Amia ; but although it was generally known that dui'ing the last part of May they appeared in large numbers in the Potomac, as well as in many Western rivers, and also in parts of the great lakes, no one had been fortunate enough to catch these fish while spawning. It was there- fore with great expectations that I sent Mr. S. W. Garman to Ogdens- burgh, N. Y., when Mr. S. S. Blodgett informed me that the garpike usually appeared on the 20th of May for the purpose of spawning. Mr. Blodgett did all in his power to make the expedition a success ; and he has not only my thanks, but will have those of all naturalists, for the aid he has given so effectually in obtaining this ichthyological prize.

The following notes by Mr. Garman describe the method of spawning : —

" Black Lake is well stocked with bill fish. When they appear, they are said to come in countless numbers. This is only for a few days in the spring, in the spawning season, between the loth of May and the 8th of June. During the balance of the season, they are seldom seen. They remain in the deeper parts of the lake, away from the shore, and, probably, are more or less nocturnal in habits. Out of season, an occasional one is caught on a hook baited with a minnow. Commencing with the 20th of April, until the 14th of May we were unable to find the fish, or to find persons who had seen them during vol. xiv. (n. s. vi.) 5

66 PROCEEDINGS OF THE AMERICAN ACADEMY

this time. Then a fisherman reported having seen one rise to the surface. Later, others were seen. On the afternoon of the 18th, a few were found on the points, depositing the spawn. The tempera- ture at the time was 68° — 69° on the shoals, while out in the lake the mercury stood at 62° — 63°. The 'points' on which the eggs were laid were of naked granite, which had been broken by the frost and heat into angular blocks of three to eight inches in diameter. The blocks were tumbled upon each other like loose heaps of brick- bats, and upon and between them the eggs were dropped. The points are the extremities of small capes that make out into the lake. The eggs were laid in water varying in depth from two to fourteen inches. At the time of approaching the shoals, the fish might be seen to rise quite often to the surface to take air. This they did by thrusting the bill out of the water as far as the corners of the mouth, which was then opened widely and closed with a snap. After taking the air, they seemed more able to remain at the surface. Out in the lake they are very timid, but once buried upon the shoals they become quite reckless as to what is going on about them. A few moments after being driven off, one or more of the males would return as if scouting. If frightened, he would retire for some time ; then another scout would appear. If all promised well, the females, with the at- tendant males, would come back. Each female was accompanied by from one to four males. Most often a male rested against each side, with their bills reaching up toward the back of her head. Closely crowded together, the little party would pass back and forth over the rocky bed they had selected, sometimes passing the same spot half a dozen times without dropping an egg, then suddenly would indulge in an orgasm ; and, lashing and plashing the water in all directions with their convulsive movements, would scatter at the same instant the eggs and the sperm. This ended, another season of moving slowly back and forth was observed, to be in turn followed by another of excitement. The eggs were excessively sticky. To whatever they happened to touch they stuck, and so tenaciously that it was next to impossible to release them without tearing away a portion of their envelopes. It is doubtful whether the eggs would hatch if removed. As far as could be seen at the time, upon or under the rocks to which the eggs were fastened, there was an utter absence of any thing that might serve as food for the young fishes.

"Other fishes, bull heads, &c, are said to follow the bill fish to eat the spawn. It may be so. It was not verified. Certainly the points under observation were unmolested. During the afternoon of the

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18 th of May, a few eggs were scattered on several of the beds. On the 19th, there were more. With the spear and the snare, several dozens of both sexes of the fish were taken. Taking one out did not seem greatly to startle the others. They returned very soon. The males are much smaller than the average size of the females ; and, judging from those taken, would seem to have as adults greater uni- formity in size. The largest taken was a female, of four feet one inch and a half in length. Others of two feet six inches contained ripe ova. With the 19th of May, all disappeared, and for a time — the weather meanwhile being cold and stormy — there were no signs of their continued existence to be met with. Nearly two weeks later, on the 31st of May, as stated by Mr. Henry J. Perry, they again came up, not in small detachments on scattered points as before, but in multitudes, on every shoal at all according with their ideas of spawning-beds. They remained but two days. During the summer it happens now and then that one is seen to come up for his mouthful of air ; beyond this there will be nothing to suggest the ravenous masses hidden by the darkness of the waters."

To Mr. Garman I am greatly indebted for the care with which he transported a quantity of garpike eggs contained in two pails which had to be carried by hand from Ogdensburgh to Cambridge, and for the arrangements made with Mr. Perry for collecting a series of eggs and of young fishes in all stages from the time of spawning until the end of July.

The present paper is, of course, merely a preliminary account, and I hope to give on another occasion a full description of the early stages of the egg, as well as a more detailed description of the changes the young undergo. Of the eggs brought to Cambridge, only thirty hatched. In my anxiety lest this attempt should fail, I did not dare to examine any of the fresh eggs; and from an external exam- ination little or nothing of the early stages of segmentation and of the development could be traced on account of the opacity of the envelope of the egg. Not one of the eggs artificially fecundated was hatched, and only a few of those laid on the angular blocks (men- tioned by Mr. Garman) lived to complete their development. The eggs were all attacked by mould, and decomposed rapidly in spite of the most watchful care. The few which did hatch, however, fully rewarded my efforts and fulfilled my anticipations. The young fish were quite hardy and flourished admirably. Of the thirty hatched in the latter part of May, no less than twenty-eight lived till the middle of July. They were exceedingly hardy, and, had it been possible to

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feed them on minute fresh-water Entomostraca, I have no doubt they would have continued in excellent condition. During the whole time of the resorption of the yolk-bag, not a single individual was lost. It was only subsequently, when they had been fed for a while on liver, that they showed symptoms of poor condition ; and finally they re- fused to eat it and languished for a few days, although at first they had eaten it apparently with great relish.

The eggs were laid on the 20th of May ; when they reached Cam- bridge, they were still semi-transparent, the yellowish-green sticky outer envelope measuring about 5mm in diameter ; the yolk- mass, of a whitish-blue color, was 3mm. In their general appearance, the eggs resembled those of toads. They were attached to the stones just as they dropped from the females, in groups irregularly arranged or isolated.

On the 28th of May, the first young Lepidosteus was hatched (Plate I. fig. 1). The young fish possessed a gigantic yolk-bag, and the posterior part of the body presented nothing specially different from the general appearance of a Teleostean embryo, with the excep- tion of the great size of the chorda. The anterior part, however, was most remarkable ; and at first, on seeing the head of this young Lepidosteus, with its huge mouth cavity extending nearly to the gill- opening, and surmounted by a hoof-shaped depression edged with a row of protuberances acting as suckers (Plate I. fig. 3), I could not help comparing this remarkable structure, so utterly unlike any thing in Fishes or Ganoids, to the Cyclostomes, with which it has a striking analogy. This organ is also used by Lepidosteus as a sucker, and the moment the young fish is hatched he attaches himself to the sides of the dish, and there remains hanging immovable ; so firmly attached, indeed, that it requires considerable commotion in the water to make him loose his hold. Aerating the water by pouring it from a height did not always produce sufficient disturbance to loosen the young fishes. The eye, in this stage, is rather less advanced than in corre- sponding stages in bony fishes ; the brain is also comparatively smaller, the otolith ellipsoidal, placed obliquely in the rear above the gill-open- ing. This is at first a mere small elliptical opening, which subse- quently becomes heart-shaped (Plate I. fig. 11) with the development of the gill-arches, one of which is formed by the anterior part of the gill-opening, while two smaller