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FAIR-MINDED critic would start a review of this work by a general verdict of praise for its compactness and usefulness. It is an excellent grammar of the Kosa language of that southernmost group of Bantu-speaking negroes known unfortunately by the most inappropriate term, the Arab word Kafir, or "Unbeliever." The group of Bantu peoples who inhabit the coastlands of the southern extremity of Africa, between the Transkei River in Cape Colony and Inhambane in the Portuguese Province of Moçambique, had better be styled generically "Zulu " rather than "Kafir" or "Kafir-Zulu."

The name Kafir (which, if it is still to be used, had better be spelt as in Arabic with the single "f") is derived from the Dutch Caffer and the Portuguese Cafre, and these again from the language of the Swahili Arabs whom the Portuguese encountered as the masters and traders of South-eastern Africa in the beginning of the sixteenth century. These Arabs, who radiated from Zanzibar northwards and southwards, called all the negroes south of the Zambezi delta Kafir" in the singular and "Kufar " in the plural, and by this name they spoke of them to the Portuguese, who at first made use of the Zanzibar Arabs as pilots and guides along the eastern coast of Africa. The Cape Dutch borrowed the term from the Portuguese, and so passed it on to the English.

The great Zulu race at the present day is divided into three main branches so far as language or dialect is concerned the Ronga or Tonga section of Southeast Africa (including the Abagaza), between Amatongaland and Sofala; the Zulus of Zululand, with their outlying colonies and offshoots in Swaziland, Matabeleland, and across the Zambezi (through British Central Africa to German East Africa); and the Kosa Kafirs of Western Natal, Pondoland, and the Transkei territories of Cape Colony. The difference between the Zulu and Kosa dialects is much less than between Zulu and Shi-ronga. Naturally, the Zulu speech that has been dropped down here and there in little colonies in East-Central Africa north of the Zambezi is already departing widely from the Zulu in Zululand, owing to intermarriage with local races.

The original place of origin in Central Africa of the Zulu-Kafir peoples and dialects is still an unsolved mystery; their nearest relations at the present day in vocabulary and grammar (though not in phonology) are the great Basuto group of Central South Africa and the Damara (Ova-herero) of South-west Africa. There is not that marked relationship with the existing tongues in Central Zambezia which one would expect to find, though, of course, as these are equally "Bantu " in form and construction they offer a good

It is more convenient to write this word, which begins with a lateral click [=//osa], with a K. It is usually spelt Xosa in South Africa.

deal of resemblance to Zulu, but not more so than is shown by the other Bantu languages of East Africa. Here and there in the dialects of Lake Nyasa and even of the tongues of inner East Africa there are hints of resemblances to the Zulu group in vocabulary. At the same time, many of the peculiar features in vocabulary and grammar of the Zulu language and its kindred dialects are only to be met with elsewhere in the Se-suto forms of speech, and perhaps in the Ochi-herero. The Zulu-Kafir language group offers some archaic features in the form of its prefixes and of certain word-roots. But it is not the " Sanskrit of the Bantu," nor nearly so archaic as the languages round Tanganyika and the Victoria Nyanza.

One of the most marked peculiarities of Zulu and Kosa Kafir is the possession of three "clicks." The Shi-ronga dialects of South-east Africa, though closely related to Zulu in vocabulary and grammatical structure, do not possess these clicks, and no trace of them is met with in Se-suto or Ochi-herero, or indeed in any other Bantu language. The general assumption is that the clicks have been borrowed from the Hotten

tots, and, of course, in the case of the Kosa Kafirs this is conceivable, as for centuries they have bordered on the Hottentot domain. Yet it is rather extraor

dinary that the Basuto peoples, who in history certainly preceded the Kafir-Zulu in the invasion of South Africa, and who, as may be seen by their physical appearance, have anciently inter-bred with the Hottentots, should not have borrowed any click from Hottentot or Bushman. Likewise the Ova-herero and their allies have been in close contact with Hottentot peoples in South-west Africa without catching the infection of the click. Miss A. Werner, one of the few serious students in Great Britain of Bantu languages, has written several articles on this subject, without, however, arriving at a definite conclusion as to whether the Zulu-Kafir clicks are borrowed from Hottentots or are independent developments of the language, recently acquired in situ. The author of the work under review seems to suggest that the three Zulu-Kafir clicks may be explosive pronunciations of the gutturals. If so, they might have developed separately without Hottentot influence.

It is a pity in the work before us that the author has not had the courage to quit South African provincialism and aim at bringing his grammar into accord with the approved classification of the Bantu languages, and a system of spelling, such as that of Lepsius, which is both scientific and logical. A strong man should come forward, and, by his influence, compel all philologists, the whole world over, to adopt the Lepsius alphabet (with two or three trifling changes) as the standard which all persons must adopt in transcribing the languages of the world not already and anciently expressed in Roman letters; nay, more, it is to be hoped one day that all the civilised tongues of the world-English, French, German, Russian, Greek, Arabic, and every other speech with a literature-may be written down in one form of lettering, and according to one standard-perhaps the Lepsiusof expressing sounds by letters.

Meantime, some uniformity of transliteration might

well be enforced in Africa. As it is, there is one method adopted in the Western Congo, another in South Africa, a third in East Africa, and a fourth in West Africa and the Sudan. Mr. McLaren, in the Kafir grammar under review, adopts the South African standard; the three clicks which Lepsius expresses by /, !, and // are rendered (as they have been for half a century) by c, q, and x.

Now throughout Eastern Africa, c or ch is used to express the palatal consonantal combination of ts which in South Africa and many West African missionary grammars is rendered by tsh; q is universally used in North, North Central, and Western Africa (besides by Lepsius) to transliterate the Arabic qof, a very explosive k, the old meaning of the Mediterranean q. X is used by the Congo missionaries (following the Portuguese) as an equivalent for the English sh (s), and by others as a convenient form of the Greek x to express the strong guttural kh (Scotch and German ch). On the other hand, kh, sh, and zh in transliterations into Roman letters of Hindustani and Arabic names are intended to be pronounced literally like an aspirated k, s, and 2. It is therefore necessary for a logical orthography to adopt c, q, and x for the purposes above mentioned, namely, to represent the English ch, the Arabic and the Greek X. Therefore it would be preferable to render the South African clicks by other signs, such as those proposed by Lepsius.

For the practical purposes of those who wish to acquire the Kafir language or arrive quickly at an understanding of its main features, Mr. McLaren's grammar may be very highly commended.

MINING LAW.

H. H. JOHNSTON.

Mining Law of the British Empire. By Charles J. Alford. Pp. xii+300. (London: Charles Griffin and Co., Ltd., 1906.) Price 8s. 6d. net.

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LTHOUGH admirable treatises on mining law for the guidance of lawyers have been written by Rogers, Walmesley, McSwinney, Bainbridge, Cockburn, and numerous foreign authors, the field has by no means been exhausted; and Mr. Alford's work forms a welcome addition to technical literature. Written with conspicuous literary skill by a mining engineer of wide experience, it gives a concise summary of the various codes of mining law of the British possessions throughout the world, with well considered remarks on their characteristics. The term mining law is taken by the author to mean the enactments that regulate the acquisition and tenure of mining rights. Mining regulations, which control the methods of working mines, receive merely incidental mention. In the case of Great Britain, it is true, the Mines Regulation Acts are quoted at some length as models; but even in this case no reference is made to the Amendment Act of 1903 or to the numerous special statutes, of which fourteen are cited in Sir C. Le Neve Foster's "Ore and Stone Mining," that affect miners and workers in open pits in this country. Indeed, Mr. Alford's chapter on the

mining law of Great Britain is the least striking in the book. Mining in Great Britain is so largely a matter of contract between lord and lessee, and so largely concerned with non-metallic minerals, that there is little scope for the comparative treatment of the metal-mining rights and obligations that forms so interesting a feature of the chapters dealing with colonial laws.

The historical study of the inception of mining law receives, as is to be expected in a book of a purely practical character, only brief mention, and the author has refrained from the temptation of citing the ancient statutes set forth in that delightful old work on mining law, the "Fodinæ Regales of Sir John Pettus, Knight (1670). Originally, the author tells us, the minerals of the country were worked by slaves or serfs for the benefit of the lords of the soil; and Mr. Alford would have added to the interest of his note on the free miners had he mentioned the fact that the last native-born Briton who was a slave in Great Britain died in the reign of Queen Victoria. When the Queen ascended the throne, many men and women were still living who had in their youth borne a legal bondage in the collieries of Scotland. Such miners received wages, but were not allowed to move away from their master's estate. They were bought and sold with the property; and although they were freed from their servitude by an Act passed in 1799, the slave taint stuck to their occupation for many years.

Mr. Alford divides his work into nineteen chapters, dealing respectively with the principles of mining law, and with the mining laws of Great Britain, British India, Ceylon, Burma, the Malay Peninsula, British North Borneo, Egypt (should not a word of explanation have been given that Egypt is not a part of the British Empire?), Cyprus, the Dominion of Canada, British Guiana, the Gold Coast, Cape Colony, Natal, the Orange River Colony, the Transvaal Colony, Rhodesia, the Commonwealth of Australia, and New Zealand. An analysis of the mining laws cited shows a grouping of the principles of their construction into two classes: (1) that in which the State or a private owner of mining property has the right to grant concessions or leases; and (2) that in which any individual, under specified restrictions, has the right to locate a certain limited area of ground or claim and to work or to dispose of it. It is surprising to learn that five-sixths of all the mining areas of the world are worked under the former system of titles. The concession system of large prospecting areas, followed by mining leases of limited areas, of which the present mining law of Egypt is an example, appears to be the most advantageous system of opening up an unexplored country.

As an authoritative statement of the conditions of tenure of mining property under various laws, Mr. Alford's book cannot fail to prove of great value to all connected with mining in the colonies. The work is most carefully and accurately done. There are, however, a few slight omissions; and in order to make the survey of the mining law of the British Empire complete, the author might with advantage

add, when a new edition is called for, a few particulars of the mining law of Newfoundland, the oldest British colony, where copper and iron-ore mining are actively carried on; of the West Indies, where, in Trinidad and Barbados, asphalt mining is of some importance; of British New Guinea, where gold mines are worked; and of Nigeria, where some tin ore is raised. BENNETT H. BROUGH.

ORGANIC CHEMISTRY APPLIED TO PHYSIOLOGY.

THE

Outlines of Physiological Chemistry. By Dr. S. P. Beebe and Prof. B. H. Buxton. Pp. vii+ 195. (New York: The Macmillan Co.; London: Macmillan and Co., Ltd., 1904.) Price ás. 6d. net. 'HE book deals chiefly with the theoretical side of organic chemistry as applied to physiology. The first chapter, of twenty-one pages, contains an account of the following matters :-dissociation in solution, nomenclature of acids, chemical equilibrium, catalysis, colloids and crystalloids, colloidal solutions of metals, aggregation, suspension and precipitation, oxidation and reduction, osmotic pressure, calculations of a formula, reasons why reactions take place, graphic formulæ, and ultimate analysis.

It need scarcely be added that the space is entirely inadequate to treat of such a heterogeneous collection of chemical problems, even were it profitable to put them in such juxtaposition. The student who has made any study of general chemistry does not need the chapter, and one who has not will scarcely be able to grasp it in the condensed and jumbled form in which it is here presented to him for the first time.

It would hence have been no loss if the book had commenced with the elementary organic chemistry of chapter ii., so as to leave all the space for this, which is the proper introduction to the subject of the book.

A description of the groups of organic compounds most interesting to the physiological chemist is given in chapters ii. to v., of the proteid molecule, its component parts and disintegration products in chapter vi., of enzymes in chapter vii., and an outline of the antitoxin theory, &c., under the title of "Disease and Immunity, forms chapter viii. and concludes the volume.

This latter part of the book is on the whole well and clearly written, but it might be made much more interesting by the authors breaking, even more frequently than they do, their intention of saying nothing about practical work. A description of organic compounds and their relationships, without any statement of what experiments the knowledge of these relationships is based upon, forms only dry and unprofitable reading. For example, it would be much better if the reader were told how the purin bases, or hexone bases, are separated, and would not have taken up a vast amount of space. Without some such instruction, these bodies are only uninteresting names which weary the reader.

The style of the authors is also such as may encourage a too-realistic belief in the mind of the junior

chemist in the graphic formulæ which form the organic chemist's rosary. Thus at the opening of chapter v. there occurs the statement, "The chains of C atoms have a tendency to curl over and join at the two ends, forming in this way a closed chain." At another passage in the volume one reads of the excretion of benzene rings." The account of the chemistry of the proteid molecule is very clear and well arranged, and this portion of the book may be recommended to the physiological chemist interested in the organic chemistry of proteids.

THIS is emphatically a text-book, deductive in method and Euclidean in arrangement; as such, it has the defects of its qualities, but its merits are undeniable. In this volume the author deals with the elementary notions of rational and irrational number, point aggregates, function, continuity, differentiation and integration. The subject last mentioned occupies pp. 333-560, so that conditions of integrability, change of order of integration, upper and lower integrals, &c., It should be receive a proper amount of attention. noted, too, that although it is confessedly incomplete, the discussion of maxima and minima of functions of two or more variables is satisfactory as far as it goes, a most unusual circumstance as things are at present. Perhaps the most valuable feature of novelty is that the author occasionally criticises arguments once thought sufficient, but now known to be fallacious, illustrating by examples the way in which the defective proofs break down. This is an excellent way of making a student feel the necessity of mastering the more refined methods of recent analysis. There is one point in which the author has not quite done justice to his authorities. After explaining Cantor's theory of irrational numbers, he gives a brief sketch of Dedekind's method of partitions, but he does not give this in its genuine form. The essence of a partition is that it divides all rational numbers (with the possible exception of one) into two classes, each element of one class being less than each of the other. After this definition it is proved that the aggregate defines a partition as dividing all real numbers into of partitions is continuous. Prof. Pierpont (p. 82) two classes; this enables him to use Dedekind's notation, when convenient, but it does not give a just idea of Dedekind's theory, and this is a pity. For bibliographical details the reader is referred to the

Encyclopädie der mathematischen Wissenschaften "; this is all very well for those who have access to that work, but in the interests of the student it would be well to give a list of the most important original sources. It ought to be said that in his preface the author acknowledges his special obligation to Jordan, Stolz, and Vallée-Poussin; at the same time it is evident that he has made use of this and other material in an independent way.

Sound and Rhythm. By W. Edmunds. Pp. xii+ 96; and Box of Models of the Human Ear. (London: Baillière, Tindall and Cox, 1906.) Price 2s. 6d. net.

THIS is an admirable little book. The elements of physiological acoustics are described with remarkable lucidity and accuracy, and there is a wealth of illustra

tion both in the text and in the diagrams. There are chapters on the nature of sound, waves of sound, musical scales, organ pipes, "time" and movement, the ear, and the voice. Nothing could be happier than the exquisite drawings by Miss Martin Mohun showing an ideal couple-a boy and girl-waltzing and drawing sound curves on the seashore. Mr. Lapidge's diagrams are also excellent. To assist the teacher six models, made by Mr. Lapidge, may be obtained for the illustration of the book for one guinea. These models show the structure of the middle ear and the chain of bones. They are accurate in all anatomical details. The box also contains a nightingale pipe, which is in miniature an adjustable stopped organ-pipe. Mr. Edmunds has succeeded in showing how science may be made interesting to young people. There is a constant appeal to observation and experiment, and the whole subject is treated in such a way as to promote the healthy development of the mental faculties in early life. JOHN G. MCKENDRICK.

Historical and Modern Atlas of the British Empire, specially prepared for Students. By C. Grant Robertson and J. G. Bartholomew. Sixty-four plates. (London: Methuen and Co., 1905.) Price 4s. 6d. net.

Philips' Model Atlas. Fifty Maps and Diagrams in Colour. (London: George Philip and Son, Ltd. n.d.) Price 6d. net.

THE first of these atlases is full of material designed to show students and teachers how intimately the studies of geography and history are related. The excellently executed plates serve as graphic objectlessons demonstrating the interdependence of cause and effect, and are skilfully conceived with a view to impress various important lessons pictorially. The atlas may be commended to the careful attention of both teachers of geography and history.

The sixpenny atlas of Messrs. Philip gives great prominence to photographic relief maps of the countries dealt with, and these plates will prove of great assistance in enabling young pupils to form mental pictures of the distribution of highlands and lowlands in the countries they are studying, thus providing them with a to understand the direction of flow of rivers, the distribution of rainfall, and other important geographical features. This wonderfully cheap atlas deserves to be used widely in junior classes.

means

Natural Science in Hygiene, or the Life-History of the Non-Bacterial Parasites affecting Man. By Dr. James Rodger Watson. Pp. vi+62. (Bristol : John Wright and Co.; London: Simpkin, Marshall, Hamilton, Kent and Co., Ltd., 1905.) Price 1s. 6d.

net.

It is stated in the preface that this little book is intended to place before the student of public health, in a convenient and realistic way, the life-histories of those members of the vegetable and animal kingdoms which by their mode of life are of importance from a public health point of view, and with which he is expected to make himself familiar.

If by "student of public health" is meant the medical man who is going to devote his life to public health, the details given, though on the whole fairly accurate and up to date, are far too meagre and inadequate to be of much service, but the diagrams of life-cycles of the parasites discussed may serve to impress the facts on the memory. The book seems to be more suited to the requirements of the sanitary or meat inspector or health visitor than of the student of hygiene. R. T. HEWLETT.

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.]

A Plea for Absolute Motion.

THE title of Prof. Schuster's letter is somewhat wider than its contents. The writer does not discuss whether the term "absolute motion" is significant, but only whether, assuming that the words have a definite meaning, the absolute motion of any body can be determined by physical inquiry. By implication he has himself answered the question in the negative, for at the critical stage of his discussion he introduces arguments which are not physical, but philosophical.

Prof. Schuster asks, 'Does it require explanation that all star groups have the same velocity vector imposed upon them? Certainly; it requires explanation no more and no less than any other distribution of velocities. It is highly desirable that the equations of the proper motions of the stars should be established and their past history traced until the physical circumstance that determined those motions is discovered. But this circumstance need not be a body at absolute rest. In the analogy which Prof. Schuster gives, the inhabitant of a gaseous molecule would be quite wrong if he decided that the rest of the

containing vessel was absolute. Accordingly, Prof. Schuster has recourse to philosophical arguments. We have determined, he says, the velocity relative to a material body which does not come within the range of our observations. I should have thought that the mere fact that we had determined a velocity relative to it proved that it had come within the range of our observations; the deduction from the motion of some of the stars of the existence of dark satellites near them seems an analogous case; and since, he continues, this conclusion is absurd, the body must be replaced by something immaterial. Why is it less absurd to determine a velocity relative to an unknown immaterial than to an unknown material substance?

Finally, since the something is immaterial, it cannot be

The

in motion, and therefore it must be at absolute rest. term immaterial may have many meanings; but I should have thought that an immateriality which precluded a substance from being in motion also precluded it from being at rest. A thought, for example, is incapable of motion, but it is equally incapable of rest; any application to it of the terms motion or rest is not true or false, but simply meaningless.

It may also be pointed out that if the "something at rest" is immaterial, the analogy breaks down. The distribution of the velocities of molecules in a gas depends on with an immaterial boundary. the collisions with the walls; but a star cannot collide

Prof. Schuster says that the attempt to make all motion relative to the æther is inconsistent. With all respect, I do not think he sees the point. The reasons for our preference of the Copernican to the Ptolemaic hypothesis are two-fold. The first reason is that the equations of motion of the solar system are simpler on the former theory. The second reason is precisely that which made the theologians object to the Copernican hypothesis; it points out that it is the sun, and not the earth, which holds a unique place in the solar system; this is a question of scientific taste. There are the same reasons for referring all motions to axes fixed in the æther-if we could determine them. Firstly, an attempt is being made to reduce all laws to electrodynamic laws, and these are simplest on the basis of a fixed æther. Secondly, the æther holds such a unique place in the physical universe that it is desirable to direct attention to the fact. The question of the "absolute motion of the æther "-if any cannot come within the range of physical discussion any more than the "absolute motion of the sun can come within the range of any discussion based on the properties of the solar system.

I should like to add a few remarks on the subject of "absolute rotation." "Rotation," it seems to me, like

"expansion" or "shear,' is not the name of a distinct kind of motion-it is only a term introduced to abbreviate the discussion of a particular and important case of the relative translation of the particles of a body. Direct kinematical statements can only be made concerning particles of infinitesimal volume; such particles can only have translation, they cannot rotate. When bodies of finite volume are considered, they are analysed into particles the motions of which are then investigated. If there is no relative translation between the particles the motion is said to be pure translation; if there is relative translation the motion is said to be partly, or wholly, rotational. It is the characteristic of rotation that two particles situated on a straight line through the "axis of rotation " possess a relative acceleration along that line, and it is by the existence of these accelerations that absolute rotation is detected. If we can find a line such that any two particles situated on a line intersecting it are subject to relative accelerations along the latter, the body is said to rotate. It would be impossible for any observer on a rigid body to detect its rotation, for the relative accelerations of its particles could not be observed. If Foucault's pendulum were rigidly attached to the earth, or if the water in Newton's bucket were frozen, no observers on the earth or the bucket having cognisance of these bodies only could detect the "absolute rotation." In fact, the absolute rotation of bodies of finite volume is only a special case of the relative translation of particles. NORMAN R. CAMPBELL.

Trinity College, Cambridge, March 18.

Interpretation of Meteorological Records.

THE series of curves given by Messrs. Lander and Smith's instruments, and published in NATURE of March 15, are most interesting, and one cannot help looking for the cause of the close relation between the movements of all the five instruments. It is with the view of offering an explanation of the sympathy between these instruments that the following lines are written. If I might venture to suggest a first cause of these movements, I would say it was the thunderstorm that drew the trigger which started all of them. The thunderstorm gave rise to a heavy fall of rain a quarter of an inch in a few minutesand this rainfall appears to have been the cause of the movement of all the instruments, and instead of being placed last in the series should have been put first. The effect of a heavy local fall of rain is to cause a down rush of air, the air being dragged downwards by the falling rain. This downward moving mass of air checks the wind, because its movement is at right-angles to the wind, hence the drop in the wind-velocity curve. The wind not being able to pursue its course gets deflected in this case the curve shows it was to the north-west. The down rush of air where it meets the surface of the earth has its velocity reduced and direction of movement changed; its pressure is therefore increased, and the barograph shows that the pressure increased by the tenth of an inch. The downward rush of air would bring the air from the upper strata to the surface of the earth, and as this upper air would be in all probability the colder, it would cause a fall in the temperature, which the thermograph shows amounted to twelve degrees.

On one occasion I had an opportunity of seeing this downward movement of air produced by local rain. It was while making some meteorological observations on the top of the Eiffel Tower, in Paris. At first the weather was fine, and the dust-counter showed that the impure city air came to that height in great quantities. After a time a heavy shower came on which reduced the number of particles in the air, and at last the air became as free from dust as any air I have ever tested on the mountain tops of Switzerland. This increase in purity could only be due to the rain dragging down the upper purer air to the level of the top of the tower, as rain cannot wash the air to anything like that purity.

If the time scale of the curves in the instruments had been a good deal wider, and all the clocks going together, one could have found out whether the above explanation

Agricultural Education and Colonial Development. IN your issue of January 11 reference is made to the requirement which has recently arisen for specialists in agriculture and the allied sciences for employment in the British colonies and dependencies. The case, so far as India is concerned, may be stated very briefly. The Government is willing to spend money in the development of agricultural education and research, but the efficient recruitment of the department-or, more properly, departments, for there are eight local governments in India and Burma, each of which will have its own separate agricultural department-is not an easy matter. The educated native of India has not hitherto devoted the interest to the study of agriculture that he has to law and medicine, and men qualified to give instruction or conduct investigations in relation to this national industry are not to be found in the country. It is quite unnecessary to raise the question as to whether they will be obtainable in the future. This is one of the great desires of the Indian Government. In the meantime, however, men qualified to fill the offices above indicated are required, and a search has to be made elsewhere. In this respect, then, India appears to be drawing upon the same market as other countries.

In my view, the description of man that is required is one possessing a thorough knowledge of principles. The conditions of tropical agriculture are so very different from those of the British Isles that it is highly desirable for the Britisher to commence work in other continents with as open a mind as possible. I am not thinking so much of the agriculturist as of the botanist, entomologist, or chemist. Just as the chemist who has made himself master of pure chemistry makes eventually the best technical chemist, and finds it, indeed, easier to apply himself to any special technology than the so-called technical chemist, so, likewise, for agriculture in foreign countries, the men who will be most useful in the future will be those who have obtained a thorough knowledge of their particular science at college without any special reference to British agriculture. J. WALTER LEATHER. Agricultural Research Institute, Pusa, Bengal, February 28.

Peculiar Ice Formation.

IN reply to Mr. James Foulds's inquiry in NATURE (March 15, p. 464) whether the prismatic forms of ice such as he has recently observed in Lancashire have been observed elsewhere, it may suffice to refer him to previous volumes of NATURE, more particularly to vols. xxxi. and xlvii., for letters from Messrs. Woodd-Smyth and McGee, also from myself. In the latter volume is an account by me of a more extended series of observations on these crystallites than previous observers appear to have made. Friability of soils is due to interstitial water. Bishop's Stortford, March 16. A. IRVING.

I OBSERVED the same formation as that described by Mr. Foulds (p. 464) on bare soil, previously soaked with water, near Champéry, in Switzerland, as winter frosts began; and I believe that I have observed it everywhere as a common phenomenon.

I take it that the wet surface is first frozen, and that, as the cold penetrates, the ice exudes from the soil much as lanoline exudes from a lanoline tube, the water expanding as it freezes, and so forcing its way out between the more compact masses of soil, lifting the frozen surface-sheet.

The first touch of sun caused the structure to break up. It struck me at the time that this was the cause of the injurious effect of frost on the surface of roads considered from the cyclist's point of view. W. LARDEN. Devonport, March 16.