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In point of fact, as may be seen on Dr. Hann's charts the Arabian Sea ; but chiefly in the fact that any tendenca for January and July, in the new edition of Berghaus's that the heated highlands of Persia may have to create “Physical Atlas,” the diversion of the trade-winds of the such an indraught is overborne by the stronger set Gulf of Mexico, northward up the Mississippi valley towards India. For the latter country reaches far downı takes place only in the summer, and is an effect of the into the tropics, and the centre towards which the monsame agency, viz. the heating of the northern continents, soon blows must be determined by the resultant of all that breaks up the high-pressure zone of the northern tropic the temperature gradients of the whole heated region into two anticyclones, one in each of the great oceans, An eastward direction having been given to the monsoon and it is the juxtaposition of the Atlantic anticyclone at the outset, its strength in that direction is greatly in and the Mexican cyclonic depression that determines the creased by the energy set free in the Indian monsooti course of the winds and the resulting rainfall. To judge rainfall. from the case of the Western Ghats, we think it may be This question is one of more than theoretical imporisafely concluded that, if there were no mountain-chain to ance. These west winds of Persia and Afghanistan are the west of the Gulf, the results would not be greatly the dry winds of Northern and Western India, and when different. All the other instances quoted, illustrative of they prevail beyond their normal limits, over the north the diversion of great currents by mountain-chains, ex- of the Arabian Sea and a great part of India itself, to the cept such as are purely local, appear to us to be really exclusion of the rain-bearing current, they bring the due to other and similar causes.

drought and consequent dearth that have made India so In treating of the monsoons, Prof. Ferrel points out disastrously 'notorious for its famines. Possibly, the exwith perfect justice that their strength depends on the planation of their abnormal extension may be looked for form of the land, and that they blow strongly only where in those oscillations of the great polar cyclonic systems the interior of the country is high and mountainous. to which Prof. Ferrel alludes at p. 339 of his work. But when he adduces Persia as an illustration of the Cyclones and tornadoes are treated at great length. negative case, we are unable to admit its relevancy. At each of these subjects occupying more than one hundred p. 199 he observes :

pages of the book; and in connection with the latter is

given the author's theory of the formation of hail, a subject " In accordance with the preceding view of the prin: which has hitherto been less understood than almost any cipal cause of monsoons and land and sea breezes, it is seen from observation that all the great monsoons and the other phenomenon of the atmosphere. It will be bes strongest land and sea breezes are found-the former in given in the author's own words :countries and on oceans adjacent to high mountainranges, and the latter along coasts with high mountains "In the ascending current of a tornado, as in that of in the background. Neither the heated interior in sum- the equatorial calm belt, or of a cyclone, the rain-drops mer of the Great Sahara of Northern Africa, nor of are formed down in the cloud region, and carried upward Arabia and Persia, which is considered the warmest re- until they become too large to be supported by the current gion on the globe, causes, during this season of the year, and so fall to the earth. . . . In a tornado, however, the any great indraught of air. It is true that at this season ascending current is often so strong that the rain is the north-westerly winds prevail a little more on the supported until, by the blending of the small drops by north-west coast of Africa and the ocean adjacent, due, no coming in contact, very large drops are formed, and the doubt, to the influence of the highly-heated desert of strong ascending currents often extend so high that these the Sahara ; but over Arabia and Persia the north-west large drops are carried away up into the region of freezing winds continue to blow almost incessantly, during June temperature. ... There they are frozen, and after having and July, away from the interior toward the Arabian been carried up and outward above to a distance from the Sea. The monsoon influence, therefore, of countries centre, where the ascending current is not strong enough mostly level, without an elevated interior, however highly to keep them up, they slowly descend, and receiving they may become heated in summer or cooled in winter, additions of ice as they fall

, as long as their temperature is not very great."

remains below zero, ... they finally fall to the earth as

solid hailstones” But the interior of Persia is a part of the great tableland of Iran, and, to quote the description of Sir Oliver The concentric coatings so commonly observed in large St. John, “its average height above the sea may be about hailstones are explained by these hailstones being carried 4000 feet, varying from 8000 or higher in certain of the again and again into the vortex by the strong indraught outer valleys to not more than 500 in the most depressed in the lower part of the storm-cloud, the theory being portions of its centre.” Its average elevation is therefore that every hail-cloud is a tornado, although it may not much greater than that of the interior of India, very much reach down to the lower atmosphere. The vapour being greater than that of the Indo-Gangetic plain, which is the condensed as water in the lower part of the vortex, which goal of the Indian monsoon, and, as a glance at the map is frozen at a higher level, and as snow in the upper part, will show, it is not deficient in mountains. The explana- each pair of coatings indicate an additional ascent througla tion of the fact that, instead of attracting the monsoon the storm-cloud. This view, which, even at first sight, from the Arabian Sea, it is itself swept by north-west and seems far more reasonable than any previous theory, has west winds-blowing, not, indeed, towards the Arabian received unexpected confirmation from the experience of Sea, but towards the lower Indus valley--must then be more than one adventurous balloonist, more especially sought for elsewhere. The true explanation appears to that of Mr. John Wise, whose fate it was to be drawn us to lie in a combination of causes. Partly, perhaps, in seven times successively into the vortex of a hail-cloud, the latitude, which brings it within the zone of the strong and carried up repeatedly until the balloon was thrown easterly current of extra-tropical regions, which, by its out at the top. The account is, unfortunately, too long right-handed pressure, must resist any indraught from for extracting.

From what has been said, it will be apparent that Prof. Flustre, Rke., Cladophora pygmæa, Rke., Pringsheimia Ferrel's book enters very fully into the many important scutata, Rke. copos enumerated in the title. Indeed, its subject-matter It may be anticipated that a fair number of the novelties cosers very much of the ground of which modern meteoro-among these so-called “German Algæ" (the title reminds logy usually takes cognizance, and in the thoroughness of one of the “Protestant trout ") may be found on our own its treatment we know of no modern work in our language coasts. that can be brought into comparison with it.

It should be mentioned that more systematic detail H. F. B. with reference to many of these is to be found in the

author's “Algenflora des Westlichen Ostsee" (Berlin, A VEW ATLAS OF ALGE.


The author very properly calls attention to the fundaAtlas deutscher Meeresalgen. Heft I. Von Dr. J. Reinke mental importance of a thorough knowledge of marine (Berlin: Paul Parey, 1889).

Algæ to fishery, since the plant world prepares by its THI "HE German Government, operating through the organs of assimilation the food of the animal world in

Kommission zur wissenschaftlichen Untersuchung the sea. The German Commission deserve the highest der deutschen Meere, has undertaken to bear the cost of praise for the enlightened view of their functions emproducing this sumptuous "Atlas” in the interests of bodied in this undertaking, and no biologist will grudge sisbery, and students of phycology have to thank an eco- the warmest encouragement to Dr. Reinke in his work. comic aspect of their study for a very remarkable addition It is anticipated that the book, when complete, will conto the literature of it. Similarly, we are indebted to the tain a hundred plates, with the accompanying text. In United States Fish Commission for the publication of these days, when the most unmitigated rubbish frequently Frod. Farlow's "New England Algæ."

comes to us with highly pretentious illustrations, the stuIt may be said at once that Dr. Reinke's “Atlas" dent has learned to be on his guard against “prepossessas a success in every way, its level being that of ing appearances.” No plate manufacture, however, can Flornet and Thuret's " Études Phycologiques." From produce the welcome impression of weight and importthe point of view of technique, the plates are splendidly ance stamped on this “Atlas,” gained to a great extent dope, and the rest of the publication is worthy of them. by the fact that Dr. Schütt and Herr Kuckuck, who have This first part contains twenty-five quarto plates, and the drawn the plates, have given us the work of skilful cext belonging to them consists of descriptions of the botanists, and not that of draughtsmen only. Age figured and special descriptions of the illustrations.

G. M. Speaking not merely from an inspection of the book, but from a knowledge of the material of much of it communicated by Dr. Reinke to the British Museum, I do

OUR BOOK SHELF. not hesitate to state that every

one of these figures has Die mikroskopische Beschaffenheit der Meteoriten erläutert great value to phycologists. They are not mere portraits

durch photographische Abbildungen. Von G. Tschermak. of Algz, taken from specimens more or less at haphazard, (Stuttgart: E. Schweizerbart'sche Verlagshandlung [E. as is too much the fashion, but they represent faithfully Koch], 1883-85.) characteristic stages in the development of the organisms Die Structur und Zusammensetzung der Aleteoreisen in point. What is commonly termed "microscopical erläutert durch photographische Abbildungen geätzter derail* fills the "Atlas," and one can hardly imagine it Schnittflächen. Von A. Brezina und E. Cohen. better done. In this portion the author (who has had the

(Stuttgart : E. Schweizerbart'sche Verlagshandlung (E. assistance of Dr. F. Schütt and P. Kuckuck) deals Die Meteoritensammlung des k.k. mineralog: Hofkabinetes

Koch], 1886-87.) prominently with the Phæophyceæ, which, it is well

in Wien. Von A. Brezina. (Wien : Alfred Hölder, known, are his particular study at present. Many of

1885.) then are types of his own discovery, and generally The above three works together provide for the student unknown to workers in this field until this satisfactory a rich treasury of information relative to the characters of introduction to them. Since they are of special import- meteorites. The first two illustrate, by the aid of photoance to our native phycologists as Algæ of the North Sea graphy, the structure and composition of the more typical and Baltic, a list is given of them :

meteoric stones and irons respectively. The work dealHalotkrir lumbricalis , Kütz., Symphoricoccus radians, including 25 large plates, and has been undertaken by

ing with the meteoric stones is complete in three parts, Rke., Kjellmania sorifera, Rke., Asperococcus echinatus, Prof. Tschermak, who had charge of the Vienna CollecVert., var. filiformis, Rke., Ralfsia verrucosa, Aresch., tion of Minerals from 1869 to 1877. Of that which relates R. clavata, Carm, Microspongium gelatinosum, Rke. to the meteoric irons only two parts have as yet apLipfortema fasciculatum, Rke., var. uncinatum, var. majus, peared, but they comprise no fewer than 24 large plates : var. fiagellare, Desmotrichum undulatum, J. Ag., D? it is undertaken jointly by Dr. Brezina, who succeeded

Prof. Tschermak in the keepership of the Vienna Collecbalticum, Kutz., D. scopulorum, Rke., Scytosiphon Þyg- tion, and by Prof. E. Cohen, of Greifswald, whose series BUS, Rke., Ascocyclus reptans, Cr., A. ocellatus, Kütz., of micro-photographs of sections of terrestrial minerals 4. baltius, Rke., A. fæcundus, Strömf., var. seriatus, and rocks is so well known. Kke., A. globosus, Rke., Ectocarpus sphericus, Derb. et Photography has rarely been applied to a more satisSak, E. Stilaphora, Cr., E. repens, Rke., E. ovatus, factory purpose than the multiplication of exact represenKjellmu, var. arachnoideus, Rke., Rhodochorton chan

tations either of transparent meteoritic sections, or of

etched meteoric irons as seen with the unassisted eye or treasioides, Rke., Antithamnion boreale, Gobi, var.

when magnified by means of the microscope. Meteoritic balticum, Rke, Blastophysa rhizopus, Rke., Epicladia falls are rarely so large that the market is flooded with

illustrative specimens; and, indeed, a good collection of scholarlike spirit by Prof. Rendall than by Penka himself, typical meteorites is inaccessible to most students. But, whose rash philological conjectures have prevented a good further, meteoric irons are very prone to deteriorate, many people from doing full justice to the weight of his through oxidation, and the perpetuation of the characters anthropological and ethnological evidence. of a freshly etched face is thus especially to be desired. The excellence of the photographs is beyond all praise. The details, whether of the chondritic structure or of the

LETTERS TO THE EDITOR. Widmanstätten figures, are most beautifully shown. A brief description of the salient features of the sections is (The Editor does not hold himself responsible for opinions es

pressed by his correspondents. Neither can ke undertake furnished with each plate.

to return, or to correspond with the writers of, rejected The third work is nominally a Catalogue of the Vienna manuscripts intended for this or any other part of NATURL, Meteorites, but, by reason of the completeness of that No notice is taken of anonymous communications. ] collection, 'is virtually a survey of the petrographical characters of the meteorites of all the known falls. The

Mr. Cope on the Causes of Variation, classification adopted is in the main that suggested by MR. E. D. Cope's letter in NATURE of November 28 (p. 79) Gustav Rose in 1864, and developed by Tschermak in is a fair sample of his writings on biological theory, in so far as 1872 and 1883. The detailed description and definition I am acquainted with them. of the groups is preceded by a history of the Vienna Mr. Cope proposes to teach Mr. Wallace and others the first Collection, and also by a sketch of the various theories principles of both logic and biology. The tone of his letter which have been proposed relative to the mode of forma- encourages a similar frankness in reply. Mr. Cope must tion of meteorites. As a result of his microscopical not take it amiss when he is charged with two of the gravest researches, Dr. Brezina supports the view that the apprehension of the matter which he is attempting to critistructural features of meteorites are due to hurried crys-cize, and no less complete ignorance of the recognized ani tallization, and not to a slow agglomeration of fragmentary | elementary facts of the branch of science to which that par matter. Dr. Brezina adds a chronological list of the ticular matter relates. I do not hesitate to assert that Mr. Cope meteorites preserved in the known collections, and also a puts forward an argument which could not possibly be enterlengthy index of names, synonyms, and localities. The tained by anyone who is acquainted with the most notorious and work extends over 126 pages, and is accompanied by four admitted facts of heredily and variation. I venture to express plates.

LF. myself thus emphatically, because it is a matter for sincere re

gret that American biology should at this moment be identified Introduction to Chemical Science. By R. P. Williams

with what is sometimes called "a school of philosophy " which A.M., and B. P. Lascelles, M.A., F.C.S. (London : Mr. Darwin. By all means let us have discussion and criticism

owes its distinction to a deliberate ignoring of the writings of Ginn and Company, 1889.)

of Mr. Darwin's conclusions, but let it be understood that those There could hardly be a more concise and well-digested who enter upon such discussion have at any rate an elementary summary of elementary chemical principles and applica acquaintance with the works of Mr. Darwin himself, if not with tions than that contained in this work. It is a manual those of Weismann and Wallace; otherwise, much time and intermediate between the natural philosophy primer and much of your valuable space will be wasted, the minute and detailed text-book, and fills the gap with the admitted facts of heredity and variation will appear

That Mr. Cope has not the necessary elementary acquaintance pointed out in the Report on Chemical Teaching of a from what follows. The discussion in which he has intervened British Association Committee in 1888. Hence, as an is one as to whether certain structural peculiarities exhibited by outline of chemical science to be filled up in greater Aat-fish are due to the transmission to their offspring of a form detail from larger works, and as an introductory text- and position of parts acquired by muscular" efforts by the book, this volume will be found exceedingly useful. The ancestors of fat-fish, or whether these given structural peci. experiments described are such as should be performed liarities suddenly appeared in the ancestors of fat-fish as a by everyone beginning the study of chemistry, and would | “congenital variation” having no adaptive relation to any efforts also serve as an excellent introduction to a course of or experiences of a preceding generation, and were advantageous qualitative analysis. In addition to the treatment of to their possessors, so that the in tividuals thus born were favoared metals and non-metals, the work includes chapters on mitted their peculiarity to some of their offspring with such

in the struggle for existence, survived to maturity, and transorganic chemistry, and others on photographic chemistry, intensification as is found experimentally to be the result of the cheinistry of rocks, and electro-chemistry. Indeed, breeding from parents both of which possess a given congenital Mr. Williams, the author of the American edition, and the peculiarity. reviser, Mr. Lascelles, may claim to have produced a The question raised is, in short, whether in this case Lamarck's most comprehensive little work, and one deserving con- hypothesis of the transmission of acquired characters is the siderable commendation.

necessary explanation, or whether the case can be explained tsy

the action of the known causes (not hypothetical causes) on The Cradle of the Aryans. By Gerald H. Rendall, M.A. which Mr. Darwin founded his theory of the origin of species, (London : Macmillan and Co., 1889.)

viz. the occurrence of congenital variations unrelated to any like The question as to the primitive home of the so-called ficution of such variations in subsequent breeding. There has

variations in parents or ancestors, and the selection and intensiAryan race has lately excited so much interest that many been bere no ambiguity--such as unfortunately arises sometimes students must have wished for a short and clear account when like questions are discussed--as to the sense in which the of the controversies relating to the subject. This is term “acquired characters " is used. It is clear enough that by exactly what Prof. Rendall supplies in the present essay, the "acquired characters” of a parent we do not mean the substance of which was originally communicated to characters congenital in the parent, but expressly exclude them ; the members of the Liverpool Literary and Philosophical it is clear that we refer on the contrary (as did Lamarck) to new Society. Prof. Rendall accepts Penka's theory that the characters acquired by the parent as the direct consequence of Aryans were a European people who, at the close of the the action of the environment upon the parental structure, and glacial epoch, followed the ice northwards, and settled in exhibited by that parent as definite measurable features. Scandinavia ; and that Scandinavia was the centre from

Now let us consider Mr. Cope's contribution to the discussion. which, at various subsequent periods, groups of the adopt Lamarck's gratuitous hypothesis of the transmission of

He accuses Mr. Wallace-who is one of those who refuse to Aryan race were dispersed. All the arguments acquired characters-of being guilty of the sin of non-sequitur marshalled by the German writer in favour of this and "paralogism." He then proceeds to make a general statehypothesis are here briefly and effectively stated. The ment, the truh of which neo-Darwinians (or post-Darwinians, philological part of the case is presented in a more or anti-Lamarckians), in common with all inen, recognize,

although Mr. Cope offensively implies that they do not, viz. post-Darwinians, and at the same time without any reasoning ** Selection cannot be the cause of those conditions which are at all to assert (as he does, not directly but by implication) that prior to selection in other words, a selection cannot explain the there is no such thing as “congeni'al variation” or “sporting," wrigin of anything." How can Mr. Cope presume to tell us is not quite satisfactory. When it is asserted that every feature this? Who has ignored it? when ? and where? Mr. Cope by which a young animal differs from the structure of its parents does not seem to be aware of the fact that the anti-Lamarckians at a corresponding age must have been acquired by one or other attach great importance to the existence of congenital variation, of the parents as actual structural features, and so transmitted as that Darwin himself has written at length on the subject, and an acquired character to the offspring, the whole world of fanciers, that Weismann has developed a most ingenious theory as to the horticulturists, farmers, and breeders, is ready with its unanimous relatium of fertilization and its precedent phenomena to this all- testimony to contradict the assertion. saportant factor in evolution.

Let me say, in conclusion, that, as Mr. Wallace has pointed Mr. Corre pats aside all that has been done on that subject, or out, Mr. Darwin did not consider that variability in a state of elz is ignorant of it, and calmly lays down the following pro. nature was either so general or so wide in its range as later position : " lr whatever is acquired by one generation were not observations and reflections lead us to believe it to be. Mr. unmitted to the next, no progress in the evolution of a Darwin studied those causes which are found by practical character could possibly occur. Each generation would start gardeners and breeders to be favourable to excessive variation exactly where the preceding one did." The full significance of in animals and plants under domestication. He showed clearly This sentence can only be apprehended when it is understood, that the resulting variations had no adaptive relation to the that Mr. Cope believes that progres in the evolution of a exciting causes, and were manisested in the structure at birth of cuncter does occur. The statement therefore amounts to this: , a new generation, and not in that of the generation subjected to (1) that whatever is acquired by one generation is transmitted to 'the exciting cause. No one has yet been ahle to give an ile eest ; and (2) that the only possible explanation of the fact ; adequate account of the frequency and range of variation of any that a new generation does not exactly resemble its parents at a number of animals or plants in a state of nature, because natural corresponding age is that the parental generation has transmitted conditions destroy, on the average, all individuals born of two to its offspring particular features acquired by it between birth parents--except two-before maturity is reached, and those two sad maturity.

are naturally selected in consequence of their adhesion to the I doubt whether Mr. Cope will find any other naturalist- specific type. even the most ardent Lamarckian-to join him in these There can be no doubt from a consideration of the facts cited assertions.

by Darwin that, whilst variation often is reduced to a minimum Weh regard to the first, it is hardly necessary to say that it in natural conditions which remain constant, natural variations lai never yet been shown experimentally that anything acquired of conditions can and do occur, which excite the germ-cell and by se generation is transmitted to the next (putting aside para- sperm-cell, or their united product, to vary as in conditions of de diseases); and as to everything (“whatever") being so domestication. There can be no doubt that there was in tassetted, every layman knows the contrary to be true. Mr. Darwin's mind the conception of a definite relation Children are not born with the acquired knowledge of their between two effects arising from changed conditions: the Pacers. If there were no other explanation offered of offspring one being the disturbance of the equilibrium of the organism varying from their parents at a like age than the hypothesis of and its consequent production of variations ; the other razsmission of characters acquired by the parents on their way being the new requirements for survival ;, in fact, there Ebruagh life by the action of the environment, this hypothetical seems to be, as it were, at once a new deal and new rules supilacation would still be quite insufficient to account for the of the game. It is not difficult to suggest possible ways in fact that the iulividuals of one brood vary enormously as com which the changed conditions shown to be important by Darwin pared with one another, a fact which points to the individual could act through the parental body upon the nuclear matter of gery (ezg.cells and sperm-cells) as the seat of the processes egg-cell and sperm-cell, with its immensely complex and there. which resul in variation, and not to the parental body which fore unstable molecular constitution, so as to bring about variais the common carrier of then all. Assuredly these broods tions (arbitrary, kaleidoscopic variations) in the ultimate product demonstrate that all the acquired characters are not transmitted of the union of the remnant of the twice-divided threads of the to all the offspring,

egg-nucleus with the nuclear head of a spermatozoon. The With regard to the second proposition which Mr. Cope's wonder is, not that variation occurs, but that it is not excessive statement contains, experimental fact is directly opposed to its and monstrous in every product of fertilization. And yet Mr. Iruth As cited by Darwin on p. 8 of the first edition of the Cope writes from the other side of the Atlantic to assert that **Origin of Species," Geoffroy St. Hilaire showed that "un there is no possible cause of departure from parental type salural treatment of the embryo causes monstrosities ; and in offspring, excepting that assumed in Lamarck's unproved, monstrosities cannot be separated by any clear line of distinc- improbable speculation !

E. RAY LANKESTER. tion from mere variations." Mr. Darwin himself was "strongly

December 7 iselined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of conception." What he

Protective Coloration of Eggs. meant by being affected” is explained at greater length in SOME years ago an idea similar to that of your correspondent, the "Animals and Plants under Domestication," where, in Mr. Grensted (November 21, p. 53), occurred to me, as regards chap. xxi, here is a long discussion of the causes of variability, the protective coloration of eggs; and, curiously enough, the the cmclustons of which are supported by an arrav of observed red-backed shrike was one of the birds whose eggs I selected facts which Mr. Cope cannot be per nitted to ignore at his for special observation. My experience has been that the ground pleasure. Mr. Darwin there gives solid reasons (as was his colour of these eggs is quite arbitrary. I fear that I cannot waat) for holding that variability results from the conditions to furnish data, as I ought; but I well remember that I found in wh ch the parents have bren exposed : change of any kind in Sussex a rather abnormally pale clutch of eggs in a very dark the codicions of life, even extremely slight changes, often suf- nest; and that I regarded this, at the time, as completely doing fice to cause variability. But Mr. Darwin's examination of the away with my hypothesis. The evidence that I got from other, facts did not lead him to conclude that the bodily characters less striking instances, told about equally for and against. actured by the parents as the result of changes were those Another egg, whose variations I watched pretty closely, was which manife-ted themselves as variations in the off-pring. On that of the yellowhammer. Apart from differences of marking, the cryntrary he showed that the effect of changed conditions, of the ground-colour of this egg varies from pure or pinkish white, cioens of nutriment, and of the crossing of distinct forms, is a to a white rather deeply suffused with purplisn-red or olive"" breaking down," as it were, of the hitherto fixed characters brown. But in this case, again, the correspondence of colour of the race, leading to the reappearance of long-1 est characters between the egg and its surroundings could not be made out at and to the appearance of absolutely new churacters, the new all satisfactorily. characters having no more (and perhaps not less) relation to the A pale and little-marked specimen of the egg of the spotted exciting cause which acted through the parent than has the flycatcher, that was brought in to me one spring at Malvern, newly-forned pattern in a kaleidoscope to the tap on the suggested to me that it would be worth while to observe the kaleidoscope tube which initiated the rea-rangement.

variations here also. But I again failed to arrive at any conFor Mr. Cope to complain of the methods of reasoning of clusion.

I am so strongly tempted unreservedly to accept the "pro- of water to the interior parts of a volcano alrealy established rective” theory, that I perhaps lay too great stress on these may sometimes cause an eruption, and, under certain circum negative instances. As a matter of fact, I suppose that the stances, an eruption of great violence; but the descent of experience of a single individual is rarely large enough to justify water through the earth's crust to depths of 20 or 30 miles so 28 any induction being made from it. I myself, for instance, have to be the initial cause of the establishment of volcanoes is not s never come across the extreme variations of the cuckoo's egg, easy to understand. The pressure of the superincumbent rocks such as Seebohm figures.

E. B. TITCHENER. at a depth of 2 or 3 miles must be so great that all cracks and 3 Museum Terrace, Oxford, December 3.

interstitial spaces would be reduced to a minimum, and at the depth of 5 miles one would suppose that none such could exist.

Several facts are known to geologists which show that all cracka Is the Bulk of Ocean Water a Fixed Quantity ? diminish rapidly downwards. One such fact is that in many Mr. Mellard Reade's criticism is perfectly sound. If the deep mines the throw of a fault diminishes with the depth ku bulk of the ocean water on the surface of the globe has always which it is followed. Another is the existence of such warm been the same, the oceans could not at any time have been springs as those of Bath, the explanation of which is supposed shallower than at present without a decrease in the area of the to be that water percolating downward (say from the Mendipa! land. Consequently, the supposition that in early geological reaches a depth at which there is less resistance to its travelling times the area of the land was larger, and the depth of the laterally than to its further descent, and that ultimately reaching oceans less, demands the further inference that the bulk of the a crack or fault, it is forced up this path of least resistance les ocean water was less then than it is now.

the hydrostatic pressure of the descending stream. When writing on the physics of the sub-oceanic crust, I saw

It is true that a residuum of the water might continue its dowthat this was a necessary consequence of the theory, but I was

ward journey, being, as it were, slowly sucked downward a far not then quite prepared to discuss it. I have since had some

as the minutest interstitial spaces extended; but what would correspondence with Prof. A. H. Green and Mr. O. Fisher on happen when it reached the lower layers of the crust? Could at the subject, and will briefly indicate the possibilities that have possibly reach and be absorbed by or dissolved in the semi-fase! occarred to us.

rock which must there exist? Captain C. E Datton has well The first suggestion made was that, if the solar radiation was expressed this difficulty. Referring to the high temperature which greater in Palæozoic times, there would be greater evaporation,

must exist at a depth of 5 or 6 miles, he says:-* At such a and as the temperature of the air would also be higher, the temperature the siliceous materials of which the rocks are comatmosphere could hold more aqueous vapour than it does now, posed are no longer hard and brittle as when they are cold, but so that we might suppose a part of the water which is now in viscous and plastic. . . . Now a crack or fissure might reach the ocean to have been then permanently suspended above it very far down into hard, cold, brittle rocks, but into soft semiMr. Fisher, in writing to me, ad nits this possibility, and even fused plastic rocks, never. Under a pressure of several miles of thinks it might be feasible to estimately roughly the amount of superincumbent strata, a crack, or even the minutest vesicle. water so suspended if the mean temperature of the ocean at any would be tightly closed ap as if its walls were wax or bratter. A period was known. But he says :-"I d) not think you could more perfect packing against ingress of water could not be con get much diminution of the oceans in this way, for, suppose the ceived." 1 present atmosphere to consist of nothing but aqueous vapour,

Even capillary action coald not come into play an der such then it would represent a layer of water about 30 feet thick conditions as these. evaporated from the earth's surface. Now, it seems hardly

Let us next consider the alternative theory saggested by Mr. probable that at a former time there should have been an amount Fisher. He claims that geologists furnish him with a certain of aqueous vapour in the atmosphere so great that the mass of amount of positive evidence for the idea that water is an essential suc'i additional vapour should equal that of all the oxygen and constituent of the liquid magma from which the igneous rocks nitrogen and vapour now in the atmosphere, and even if there have been derived. Passing over the proofs of the existenze of was this amount, it would take off only about 30 feet of water water in the crystals of volcanic rocks and in the materials of from the surface of the globe," or abɔut 37 feet from the present deep-seated dykes, let us come at once to granite, a rock which surface of the oceans.

can only have been formed at great depths and under great If, therefore, the bulk of the wa er on and above the surface pressures, and which often forms large tracts that are supposed of the earth has remained the same since the time when the to have been subterranean lakes or cisterns of liquid matter in crast was first formed, it seems difficult to find any means of direct communication with still deeper reservoirs. Now, all sensibly diminishing the amount of water in the oceans. But granites contain crystals of quartz, and these crystals include need we make this preliminary assumption, and is it not really numerous minute cavities which contain water and other liquids : possible that there has been an increase in the bulk of surface and the quartz of some granites is so full of water-vesicles that water, and not a decrease by absorption, as some theorists would Mr. Clifton Ward has said: "A thousand millions might easily have us think? May we not suppose, in fact, that water-sub- be contained within a cubic inch of quartz, and sometimes the stance has always existed in the interior of the earth, and may contained water must make up at least 5 per cent of the whole it not, by its constant and gradual escape, have always been volume of the containing quartz." This amount only represents adding to the bulk of the surface waters ?

| the water that has been, as it were, accidentally shut up in the This idea had occurred to Mr. Fisher so long ago as 1873, and granite, for some was doubtless given off in the form of steam the following passage occurs a paper then published (Trans. which made its way through the surrounding rocks. Camb Phil. Sic., vol. xii., Part 2 p. 431): "If such was the It is therefore generally conceded that granite has consolidated condition of the interior in the early stages of the cosmogony,

from a state of igneo-aqueous fusion, and that the liquid magna a large portion of the oceans now above the crust may once have from which all granitic intrusions have proceeded contains wwerbeen beneath it”; and in the new edition of his " Physics of substance. It is therefore only a step further to assume that this the Earth's Crust " he further discusses the manner in which water-substance is an essential constituent of the liquid satsthis water-substance may be diffused through the magma of the stratum, and to suppose that it has been there since the con liquid substratum beneath the crust.

solidation of the earth. That there is no inherent improbability As a matter of fact, it is well known that almost all volcan pes, in this supposition, and that it is not inconsistent with chemical when in eruption, emit large quantities of steam, and the pre- views of cosmogony, Mr. Fisher has shown at the end of his sence of this steam has always been connected with the cause chapter on the ** Liquid Substratum." of volcanic activity. There are only two ways of accounting

I an only now concerned with it as an explanation of the for the presence of this steam : (1) that water from the sea or secular increase in the balk of the ocean waters which is from the rainfall gains access to the deep-seated foci of volcanic demanded by my theory of the evolation of continents and action ; (2) that the water-substance is a primary constituent of oceans. We can prove from the geological records that volcanic the liquid mag na below, and that when this material is forced action has always been in operation fron the very earliest tines up to the surface, the pressure which kept the water in solution in the world's history, and if it is true that such a reservoir of or combination is removed, and it is blown off as steam. water-substance has always existed in the earth's interior, the

As regards the first possibility, there are great difficulties in continual volcanic eruptions must have constantly added water the way of supposing that surface water can find its way to to the oceans on the earth's surface. llence, as I stated in my any region where the heat is sufficient to keep rock constantly in a liquid condition. It does seem possible that the access ton, 1889.

"Volcanoes," by C. E. Dutton, in Crdnance Notes, Na 343, Washing

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