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it is clear that the right way to solve the problem is for local authorities and School Boards to push ahead, as we believe they can do without fear. The list read by Sir Henry Roscoe at the opening of the proceedings shows what progress in this direction has already been made towards adopting the Act, and the Conference can hardly fail to result in a still more vigorous attempt to make a wise and extensive use of its provisions.

AMERICAN ETHNOLOGICAL REPORTS. Sixth Annual Report of the Bureau of Ethnology to the Secretary of the Smithsonian Institution, 1884-85. By J. W. Powell, Director. (Washington: Government Printing Office, 1888.)

FR

ROM the introductory remarks of the Director of the Bureau, we learn that the results of the research prosecuted among the North American Indians, as directed by Act of Congress, were of special interest during the continuance of the work in the fiscal year 1824-85.

As in forme years, the labourers in the mound explorations were remarkably successful, more especially in the territories east of the Rocky Mountains, where Prof. Cyrus Thomas, in 1885, and his coadjutors, Messrs. Middleton and Thing, subsequently, made important finds in Indian pottery, which were unique of their kind. Even more valuable are the results of the explorations carried on in New Mexico by Mr. and Mrs. Stevenson, the latter of whom succeeded in obtaining the largest and most important collection extant of objects relating to the sociology of the Zuni tribes. This rare treasury of Indian relics includes specimens of woven fabrics, pottery, stone implements, both ancient and modern, pictured urns, shrines, altars, sacred masks, fetishes, plame sticks, and other objects connected with the ancient mythology and religious practices of these people. Owing to the great variety of the objects, their true character cannot be determined without prolonged investigation, and in the meanwhile they have been deposited in the U.S. Museum, where they await their final classifcation. According, however, to Mr. Curtis, these, as well as the still more numerous collections of pottery, stone implements, and other objects, amounting to 4000 specimens, which have been obtained in New Mexico, all belong to the indigenous arts and industries of the ancient tribes who occupied the almost unknown tracts of Central America in which the Pueblo Indians are now Jocated.

In the department of linguistic research, prosecuted by the various employés of the Bureau, none have perhaps been more successful than Mrs. Ermine Smith, who was fortunate enough to discover two Onondaga MSS., and one MS. in the Mohawk dialect, all of which she has annotated and translated with the assistance of a half-caste of Tuscaroran descent. The origin and history of these MSS. are not distinctly known, but it is conjectured that they are copies of originals which have been lost or destroyed. In their present form, they are, however, alike interesting from a sociological and a linguistic point of view, for while the Mohawk MS. gives an account of the religious rites and chants of the Iroquoian League

which represented the elder members of the entire nation, one of the Onondaga MSS. records the ritual in use among the younger members of the same council, and the other the form of address used by the chief Shaman on the initiation of a newly elected chief.

These curious records have been turned to good account by Mrs. Smith in the completion of her Tuscarora dictionary, and in filling up her vocabulary for the “Introduction to the Study of the Indian Languages" now preparing for publication.

In the Far West, and especially in California, the results of linguistic field work are not equally satisfactory; and in the latter province, it would appear from the report of Mr. Henshaw, who was charged with the inquiry, that a number of the native dialects are extinct. Only a month before his arrival, an old woman had died who was the last person to speak the language of the Indians of Santa Cruz. The search for still surviving members of the several families of Indian languages current on the arrival of the Spaniards has not, therefore, begun too soon. The general results of these linguistic researches are embodied in a work entitled "Proof-Sheets of a Bibliography of the Languages of the North American Indians." This volume, a quarto of more than 1100 pages, was compiled by Mr. Pilling, and issued in 1884 by the Institute, which, with its usual liberality, has distributed the hundred copies printed to other public institutions, and to the various collaborators in the work.

In turning from the highly interesting explanatory remarks of the Director to the various monographs contained in the volume before us (a folio of more than 800 pages), we have first to notice the comprehensive and profusely illustrated treatise of Mr. Holmes, "On the Ancient Art of Chiriqui on the Isthmus of Panama."

Here the author supplies the technologist with an exhaustive history of the rise and development of plastic and textile art in this part of the continent, while he also treats fully of the literature and geography of this hitherto little-known province, whose position between North and South America imparted to the people some of the characteristics of the civilization of both sections of the western hemisphere.

Almost the whole of the enormous mass of clay and metal objects found in Chiriqui was extracted from tombs in the various huancals, or cemeteries, which are scattered over the Pacific slope of the province. These were first made known to science by Mr. Merritt, the director of a gold mine in Veragua, who, on hearing of the accidental discovery of a gold figure in Chiriqui, visited the district, and published a report of his explorations in 1859. From him we learn that in 1858, after it became known that a golden image had been discovered at Bugava, more than 1000 persons flocked to the spot, who it was estimated had in that year collected 50,000 dollars' worth of gold from one cemetery alone, which had an area of only 12 acres. A curious fact connected with the plastic decorations of the Chiriqui vases and other objects is that no vegetable forms have served the artificers as models, animals alone having been used for the purpose, as crocodiles, armadillos, monkeys, lizards, alligators, owing probably to their zoo-mythic conceptions of their divinities. Among the various groups of vases, the one comprising the so-called "alligator ware is the most interest

ing; this animal being not only represented as a surface ornament, but serving as a model for the form of such dissimilar objects as whistles, rattles, tables, stools, jars, vases and other utensils. Occasionally the human figure appears under some grotesque form, and less frequently it is used to represent a divinity. According to Mr. Holmes, the entire system of the scrolls, frets, and other devices used in Chiriqui art have been derived from various parts of the body of an animal, probably the alligator, and he regards this system of ornamentation as indigenous to the district. In a separate article, the author treats of textile art in its relations to the development of form and ornament, and more especially with respect to the industries of the early American people.

The article on the Central Eskimo, by Dr. Franz Boas, although complete and admirable of its kind, has comparatively little interest for the English reader conversant with the results of Arctic research, since a very large and important part of the information given has been derived from the narratives of Franklin, Ross, Parry, and other more recent British explorers. Yet some additions have been made to our older knowledge of the Eskimo by Dr. Boas, who gives much interesting information regarding their tribal laws and customs, the musical art of the people, and their capacity for drawing; while he relates several curious tales and traditions, which present so remarkable a similarity to those of the Greenlanders and the Behring Straits' tribes as to make it probable that all these people are of one race.

The Rev. O. N. Dorsey, to whom the Bureau is indebted for the compilation of seventeen vocabularies of the different dialects used by the Oregon Indians, adds an interesting contribution to this volume, in which he describes the results of his visit, in 1883, to the Osages in the Indian Territory. During his short stay he obtained information regarding the existence of a secret society of seven degrees, in which a knowledge is preserved of the grades and general history of the various gentes and subgentes, with their taboo and names which are regarded with reverence and not spoken of. Owing to the strict secrecy usually maintained by members of this society, it was with extreme difficulty that he induced two of the initiated to recite to him the traditions referring to the mythic history of their tribe, which had been imparted to them on their initiation. These traditions, which the author gives with an interlinear translation, record the passage of the primæval Osages from higher worlds before they bore the semblance of birds, or had acquired from a beneficent red eagle the bodies and souls with which they alighted on the earth. The sacred chart on which their descent was symbolized by a river flowing beside a cedar, the tree of life, surrounded by sun, moon, and stars, was observed by Mr. Dorsey to be tattooed on the throats and chests of some of the elder men ; but the younger Osages knew nothing of such symbols, and he was asked not to speak to them on the subject. From all he saw and heard among these and various tribes of Iowa and Kansas, he believes that in this traditional record of the descent of their gentes from different birds and animals, we have a clue not only to the names by which they are distinguished, but to the meaning of the chants and war-songs which only members of the seven degrees of their sacred societies have the right to sing.

It would appear that an arrangement by sevens is common to various kindred tribes, and there is reason for assuming that wherever mythic names or taboos are in use there are, or have been, secret societies or mysteries, which have been derived from early traditional history. In an elaborate article by Prof. Cyrus Thomas, entitled "Aids to the Study of the Maya Codices," we have an interesting account of the far-famed Maya Codex, which was acquired by the Royal Library of Dresden in 1739, and a large portion of which was collated for Lord Kingsborough's great work on "Mexican Antiquities," of which it forms the larger part of the third volume. According to Dr. Thomas, this unique document consists not merely of one, but of several original MSS., while it presents no evidence, as often asserted, that its symbols, figures, and signs are to be accepted as alphabetical, or phonetic, characters, its series of dots and lines seeming to indicate a close relationship with the pictographic system in use amongst the North American Indians. He is of opinion that these series have a chronological significance, based on the method of counting time common to the Mexicans and Mayas, in which a religious, or hierarchical, cycle of 260 days was recognized, as well as the solar year calendar of 360 days in use among the people. This interpretation must, however, for the present rank as merely conjectural, although his elaborate analyses of the Maya symbols cannot fail to be of use to the few interested in the solution of the curious philological problem involved in the elucidation of this unique codex, to which special notice was first drawn by Alexander von Humboldt. His acquaintance with ancient South American MSS. enabled him to show that, while its symbolic characters presented a close affinity with those used by the Mexicans, the material of which the MS. was composed was the Mexican plant metl, Agave mexicana.

EXACT THERMOMETRY.

Traité pratique de la Thermométrie de précision. Par Ch. Ed. Guillaume. Pp. xv. and 336. (Paris: GauthierVillars, 1889.)

THE

HE thermometer, practically as we now have it, is an instrument several centuries old, and by far the most popular of all scientific apparatus. Yet probably much less is generally known about it than about its companion implements the barometer and the telescope. The reason for this want of knowledge lies doubtless in the fact that the common use of the thermometer is chiefly for rough observations on the temperature of the air, and for this the ordinary instruments are sufficiently accurate as they leave the maker.

Meteorologists and physicians, however, occasionally have the zeros of their thermometers tested; and, for factory work, other points have sometimes to be examined. But in chemical and physical laboratories, investigations not unfrequently require that thermometers should be corrected with all possible delicacy, if the resulting measurement is to be exact and valuable. For such operations there has hitherto been no exhaustive guide; and M. Guillaume, whose ample experience in the Bureau international des Poids et Mesures is a guarantee for the practical value of what he writes, has done good service by issuing the present work at an opportune moment.

It is natural for a "Traité pratique" to refer mainly to the mercurial thermometer; for the great majority of practical thermometric measurements lie within its scope. Having a range from -40 to at least 360° C., and a possible sensitiveness of about o`001, it rarely has to be exchanged for more delicate or larger-scaled appliances. Even the air thermometer-a sort of general appeal court in measurements of heat-is always accompanied by a number of ancillary mercurial thermometers.

To begin at the beginning (which, by the way, the author has not done), a thermometer has to be made; and the method of making it has a serious influence on the result. One maker will overheat his glass, and thus

make the bulb harder than the stem; another will leave irregularities in the bulb which will cause the zero to rise Irregularly; a third can never perfectly "deprive," as it is termed, the stem of air; the breath of a fourth is constantly leaving fatty matter in the capillary tube. In short, there are endless variations in technique, to which, for delicate instruments, attention should be drawn.

The division of the thermometer is, as might have been expected, well described; and minute details of calibra

tion (chiefly by the method of broken threads) are duly set forth. Then follows a notice of a less familiar correction-that, namely, which depends on internal pressure when the thermometer is in a vertical position, and that which is produced by the (external) pressure of the air. Two methods of ascertaining the thickness of the bulb are given, but they are both inferior to Stokes's, which turns upon measuring angularly the distance between a spot on the outside of the glass and its reflection from the inner surface. Then ensues a description of the usual apparatus for determining the zero (which M. Guillaume seems to read somewhat too soon after minersing the bulb in the bath); and the method of ascertaining the boiling-point of water accompanies this. In the comparison of thermometers, which is next treated, the present writer prefers an air current to the metal plunger figured on p. 125.

If we observe the zero of a thermometer soon after manufacture, and subsequently at frequent intervals, we shall find that it is continually rising. The late Dr. Joule observed this ascent in one of his thermometers for more than seven-and-twenty years. There can be no doubt that it is due to a kind of setting of harder silicates in presence of softer or more viscous silicates in the mixture of which the bulb is composed. The softer glasses show it more than the harder ones; but in all exact work, it has to be determined and allowed for. This variation takes place at the ordinary temperature. If now we heat the thermometer moderately (say to 100) and cool it, we shall notice a temporary depression due to a temporary set. If, again, as is often the case in factory work, we heat the thermometer for a long time to a high temperature (say 180°) the glass of the bulb (especially if soft; will become sensibly more plastic; and will sometimes yield sufficiently to external pressure to cause an ascent of 6. At higher temperatures the ascent is still greater. Measurements of zero are therefore exceedingly important, even for moderately accurate work, and the author does not fail to draw minute attention to them. We should have been glad if at this point he had said something about the form of thermometer bulbs. Bulbs,

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(N is the length in degrees of the exposed column, t is its mean temperature, and a is the difference between the expansion coefficients of glass and mercury.) There can be no doubt that this correction gives too low a result at high temperatures. It has been shown that if instead of a we simply write (a +ẞN)—calculating a and ẞ from the results the demands of experiment are fulfilled with all desirable accuracy. The author, however, is disposed to leave the reader pretty much to his own devices for this correction.

voted to the comparison of the mercurial with the gas thermometer, and the measurement of dilatation of solid bodies: there are some valuable tables at the end.

The remainder of M. Guillaume's work is chiefly de

A perusal of this "Traité pratique" will perhaps cause some regret that in most of our measurements of temperature we should be obliged to employ a material that is constantly undergoing physical change, and that necessitates in instruments constructed of it so many corrections. It is, on the other hand, a fortunate circumstance that we have in the mercurial thermometer an admirable means of establishing and measuring the corrections necessary to be imposed wherever glass is accurately worked with. For it cannot be too emphatically pointed out that every lens, cylinder, flask, or other glass instrument we employ is more or less amenable to these corrections. M. Guillaume's work, therefore, should command, as it deserves to command, a very wide interest. EDMUND J. MILLS.

THE FAUNA OF BRITISH INDIA. The Fauna of British India, including Ceylon and Burma. Edited by W. T. Blanford. Vol. I. Fishes. By Francis Day. Pp. 548; 164 Figs. (London: Taylor and Francis, 1889.)

THE

HE first volume of this, the last work of the wellknown Indian ichthyologist, Francis Day, was issued under particularly painful circumstances, viz. almost on the very day of the author's death. The state of Mr. Day's health during the last few months had prevented him from attending to the correction of the proofs beyond the middle of this volume, which deals with the Chondropterygians, the Physostomes, and the Acanthopterygian family Percida; and the task of carrying the remainder through the press has fallen on the editor. This work is but a condensation of the author's quarto "Fishes of India," completed in 1878, so valuable for the copious and beautifully-executed lithographic plates which accompany it. And, fortunately, a number of these excellent illustrations (one for every

genus) have been reproduced, intercalated in the text, in a manner which is highly creditable to the Lithographic Etching Company.

Considering how much remains to be done in the investigation of the fish-fauna of India and its British dependencies, it is a matter of regret that so little attention has been paid to the subject since Mr. Day's departure from India. The supplement to the "Fishes of India," published in 1888, records no more than sixty additions to the number of species, a figure which might easily have been doubled in the same lapse of ten years but for the unaccountable want of interest shown in this most important branch of study. As an example of the results which may be attained by an enthusiastic collector in those regions, we may allude to the collections of fishes brought together during the last three or four years by Mr. Jayakar, a surgeon stationed at Muscat, at the entrance of the Persian Gulf, and presented by him to the British Museum, by which no less than twenty-five species, many of large size and of commercial importance, have been added to the record of the fishes of the Indian Ocean. It is to be hoped, therefore, that this new and well got up issue of the "Fishes of India" in a more portable form will give a fresh stimulus to the study of that fauna. A little more, however, might have been done to facilitate the identification of species, a particularly arduous task, the difficulties of which would have been greatly lessened by the preparation of satisfactory "keys." Such as they appear in this work, viz. mere abbreviated tabulations of characters, without or with scarcely any groupings under special headings, the synopses fail in their object, and it is really a matter of regret that the editor did not bring his influence to bear for a thorough recasting of this portion of the work, especially in the case of such extensive genera as Barbus, Nemachilus, Lutjanus, or Serranus, where the work of identifying species by means of the synopsis given is perfectly discouraging. With the enormous multitude of species which our present knowledge requires us to grasp, it is of primary importance that every possible facility should be given to the naturalist who uses a manual of this kind, which after all is intended chiefly for those who have but an elementary knowledge of the special subject.

The above notice was in type when we received a copy of the second and concluding volume (509 pp., 177 figs.). We are glad to see that the editor has, in many cases, recast the synopsis of genera and species. The total number of fishes known from Indian waters is given as 1418.

In concluding, we congratulate Mr. Blanford on having, under difficult circumstances, so successfully brought out this portion of the "Fauna of India"; and we join in his tribute to the memory of the late author, who, as he justly says, has rendered signal service to Indian zoology.

OUR BOOK SHELF.

La France Préhistorique. Par Émile Cartailhac. (Paris: Félix Alcan, 1889.)

THIS volume forms one of the well-known series, "Bibliothèque Scientifique, Internationale," published under the direction of M. Ém. Alglave. The subject,

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we need scarcely say, is one with which M. Cartailha is eminently competent to deal, and all who are interested in the study of prehistoric times will be glad t have so compact and lucid an account of the facts t which the work relates. He begins with a good sketch of the rise and progress of modern ideas with regard to primitive civilizations and the antiquity of the human race; and this is followed by a discussion of the que tions connected with man's place in Nature, his orig.. tiary period. An admirable chapter is devoted to the and the supposed traces of his existence during the Terstriking manifestations of artistic impulse by men of the Paleolithic age. The monuments of the Neolithic er in France are grouped with perfect clearness, and M. Cartailhac has not failed to do justice to any one of the various questions which these monuments have forced upon the attention of students. The scientific value of the book is enhanced by the fact that he avoids as much as possible the use of purely hypothetical reasoning When he comes to sets of phenomena which cannot be simply and naturally accounted for, he thinks it better to offer no theory at all than to suggest purely conjectural explanations. The illustrations, although in no way remarkable, will be of considerable service to readers who have not made themselves familiar with the aims and methods of archaeological science.

Experimental Science (Elementary, Practical, and Experimental Physics). By George M. Hopkins. New York: Munn and Co. London: E. and F. N. Spon, 1890.)

THE subject of experimental physics is here set forth in a manner calculated to afford to the student, the artisan. and the mechanic, a ready and enjoyable method of acquiring a knowledge of this fascinating subject. Although the popular style adopted by the author perhaps makes the book better suited to the general reader than to the student, it may safely be said that all classes of readers will find much to interest them. All the subjects usually included in the comprehensive term "physics" are discussed; and, in addition, photography. microscopy, and lantern manipulation. By carefully performing each experiment at the time of writing the description, the author guarantees certain success if his instructions are followed. There is an excellent chapter on "mechanical operations," containing many valuable hints on glass working, simple apparatus for laboratory use, soldering, and moulding. Mathematical expressions are almost entirely excluded.

The book is chiefly remarkable for its hundreds of excellent illustrations, very few of which are diagrammatic. Many of them, like a considerable portion of the text. have already appeared in the Scientific American, which is alone sufficient guarantee of their quality. Some of the latest inventions, including Edison's new phonograph, are described and illustrated.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE, No notice is taken of anonymous communications.]

not.

"Modern Views of Electricity."

THE only point really at issue between Prof. Lodge and myself seems to be whether the difference of potential between two metals in contact can be measured by the Peltier effect or He asserts that he regards the statement that it can as an axicm, while I maintain that the only reason for calling it an axiom is that it cannot be proved. Let us take a simple case Suppose we have a condenser, the plates of which are made of two different metals metallically connected, and that this con

denser is placed in a vacuum, then, so far as I can see, Prof. Lodge & principle must lead to the conclusion that the difference if potential between the plates of the condenser is proportional to the Peltier effect; but if this is so, it is quite easy to show by the second law of thermodynamics that if the system is regarded 2 a neat engine, the Peltier effect cannot vanish except at the zero of absolute temperature.

On the other points mentioned by Prof. Lodge in his letter, there does not seem sufficient difference of opinion between us to make it worth while discussing them.

In conclusion, let me assure Prof. Lodge that I am thoroughly in sympathy with the view that the consideration of the behaviour of the medium in the electric field is absolutely <sential. I do not think there is anything inconsistent with this in the paragraph he quotes, which was intended to express what is well known to have been the opinion of Maxwell himif that the key to the secret of electricity would be found in **vacuum tube. THE REVIEWER.

'ne

The Physics of the Sub-oceanic Crust.

1 your article on the above subject in NATURE of November 21 (p. 54), the important proposition that the earth's crust rests on a liquid layer is once more brought to the front The question reaches to the very basis of geology, but, like roost of those of real importance, is not now recognized by the Society which occupies apartments in Burlington House, real free, for the purpose of forwarding the study of geology. Nothing is more obvious to the geological student than that eporous thicknesses of strata have been formed at practically the level. We do not find that, when a thousand feet of sedi ment has been deposited under water, the deposition began in water which was 1000 feet deep, and went on gradually lessenng the depth until the sea or lake was filled up; but we do find, a the coal measures, that the entire 1000 feet was deposited an most uniformly shallow water; that therefore the crust of the earth must have sagged foot by foot as additional feet of burdens were laid upon it. Deltas that have not yet been bottomed show handreds of feet of silt, every yard of which was deposited at only a few feet from the surface level of the water; estuaries and river valleys slowly sink where there is sedimentation; ice-caps tell of accumulation accompanied by depression and submergence, and re-elevation when the burden is melted and dissipated; coral formations and submergence are regarded as well-nigh septranie, and even lava flows flowing on to a plain have werk is level in a degree corresponding with their mass. Where there is fifty or a thousand feet of piled-up lava-sheets you may look for a fault of like amount on its flanks, like that which, still unsuspected by geologists, cuts the Isle of Mull in half. Whether we look at the past or the pre-ent, we seem to see evidence of a crust resting in equilibrium on a liquid layer, and sensitive to even apparently insignificant readjustments of its wer bt. And if the crust did not respond to, and make room for, the burdens laid upon it by the removal of disintegrated ind and its redeposition as silt under water, would not the seas be choked for miles found every coast? The abrading action of the waves cuts down the land, be it high or low, to a dead ur firm level, and sooner or later it must become first beach, an I then sea-bottom. There it is covered with silt or sea-weed, and is no longer abraded, and would, therefore, form great level tracts, astead of almost uniformly shelving coasts, unless it sieidel Arri A to the increasing weight of sediment and water. The immediate effect of cutting down cliffs, say of 100 feet in height, and removing them in solution or by wave action, Is to relieve the pressure at their base; and I claim that, wherever I have excavated for the purposes of collecting under such conditions, I have found a decided slope inwards away from the sea, if the strata were at all horizontal, no matter what direction their general inclination might be at a distance from the sea zoargin. But on the beach, a little way from the base of the cliffs, the slope is, on the contrary, towards the sea, and whatever the general inclination may be, we see the harder ledges, even if but a few inches thick, sloping away into deeper and deeper water until lost to view; and if you choose to follow them and dredge, you trace thein tending downwards into yet deeper water. This appears to me to be simply because the relief from pressure has made the beach-line the crown of a slight arch, and an arch that continues to grow and travel, else how could we collect day after day and year after year, on the same spots, such as Lastwire or Bracklesham Bays, fresh crops of fossils after

every tide? I have hundreds of times picked up every vestige of a fossil on perhaps an acre of Eocene or Gault, yet a couple of tides have removed so appreciable a layer that the area has appeared studded with fresh specimens that were twenty-four hours previously wholly covered and concealed under matrix. Yet this ceaseless waste does not lower the level of the beach as it ought to.

And if such slight displacements as result from coast denudation have so appreciable an effect, what must take place in ocean, if subsidence is going on, and the weight of water on the increase? Darwin saw that the vast rise of land, which he so graphically describes in South America, must have been accompanied by a corresponding depression in the bordering oceans; and in turning his pages you almost expect to come on the view that depression in the Pacific must be the cause of the upheaval of the coast-line. It only wanted the liquid layer theory to make the dependence of one on the other obvious. No general rise of land has, or ever can, take place, under the overwhelming pressure of the great ocean depths, and oceans are thus permanent; the struggle is confined to whether the liquid layer shall overcome lateral resistance and find relief along the coastlines, which are the nearest lines of least resistance, and already weakened by abrasion, forming coast ranges, or rending the crust, and pouring over thousands of square miles from fissure eruptions; or whether it shall overcome vertical resistance, and raise the beds of shallower ocean eventually, perhaps, into land. Thus the tendency, as noticed by the writer of your article, is for deep oceans to become deeper, under pressure which may increase but never relaxes, and for mountain-chains to grow into higher peaks, the more weight is lessened by valleys being cut up and denuded.

This theory accounts for innumerable facts in the physics of the earth which space would not permit me to enter on, and is, so far as I know, opposed to none. J. STARKIE GARDNER.

Area of the Land and Depths of the Oceans in
Former Periods.

IN a letter to NATURE (p. 54), entitled " Physics of the Suboceanic Crust," by my friend, Mr. Jukes-Browne, the following passage occurs :

"We are at liberty to imagine a time when there was much more land than there is at present, and when all the oceans were comparatively shallow."

I wish to point out that such a condition of things could not obtain if the bulk of the ocean water was the same as now. To

get more land, the ocean would have to be deeper than now, not shallower. An easy way of conceiving the effect of shallowing the oceans is to mentally lift up the present ocean-floors, the result being an overflow of water and decrease of land area. The only possible way of shallowing the oceans and increasing the area of the land would be to make the ocean-floors perfectly flat, and to surround the continents with vertical walls of rock -in fact, to make the oceans into docks, which nevertheless would exceed two miles in depth.

I pointed out this geometrical fact in "Oceans and Continents"—an article which has provided some of the stock arguments against their fixity. If, therefore, theorists feel it necessary that the land areas should be greater, and the oceans shallower, in former ages, they are bound at the same time to provide some means of decreasing the bulk of the ocean waters. This seems difficult, as other theorists tell us that the amount of water on the globe goes on decreasing, being used up in the hydration of the crust of the earth, and point to the condition of things on the moon as the final stage of our planetary existence. T. MELLARD READE. Park Corner, Blundellsands, near Liverpool, November 23.

Distribution of Animals and Plants by Ocean Currents.

Sous ce titre, vous donniez naguère (vol. xxxviii. p. 245) une correspondance de M. A., W. Buckland concernant divers phénomènes observés à Port-Elisabeth, dans l'Afrique du Sud. Entre autres choses il y était relaté que, vers la fin de l'année 1886, un fruit analogue à celui du cocotier avait été porté par la mer sur le rivage de Port-Elisabeth en même temps que des quantités considérables de pumites ou pierres-ponces.

Geological Magazine, 1880, p. 389 also, see letter in same magazine, 1381. p. 335, headed subsidence and Elevation."

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