The physiographical part is the better, but the limitations which Prof. Gregory applies to geography have hampered his treatment of the rest of the book. The land forms (a better term than earth forms) are accurately described, but although in his lecture he vigorously insists on the fact of facts in geography

66

LIQUID FUEL.

Liquid Fuel and its Combustion. By W. H. Booth. Pp. xx+411. (Westminster: Archibald Constable and Co., Ltd., 1903.) Price 24s. net.

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sea, its movement through the air, as invisible aqueous vapour, its concentration in clouds, and its fall as rain," he practically ignores climate in his descriptions of the different countries. He loses more than half the educational value through this neglect. Climate and configuration are equally indispensable fundamental factors in geography.

We agree with him when he protests against the idea that anthropology, zoology, botany, astronomy and geology are but branches of geography. This is not the geographer's point of view. The misconception is due to the confusion of the old South Kensington physiography-a useful introduction to elementary science, mainly physical, especially in its cosmical and terrestrial aspects-with geography. This physiography, as Prof. Gregory points out in his preface, gave a valuable training to many a teacher of geography, and helped to expel deep-rooted fallacies and misleading expressions which were (and to some extent still are) to be found in many geographical textbooks. We fear that Prof. Gregory believes that geography consists of two parts, a physiographical part which is scientific, and a topographical part which is purely descriptive.

We have no wish to undervalue the descriptive aspect of geography, but this does not involve a rejection of geography as a branch of science. Prof. Gregory, and those who think as he does, have not yet shaken off the effects of their own schoolboy experiences. They have not seen the world as composed of a number of very complex associations of rock, water, air, plant, and animal, including man, which may be classified generically and specifically as readily as the organisms which they contain. The aim of the geographer, like that of the botanist or zoologist, is not confined to observing and describing phenomena, but includes comparison, classification and interpretation. It is a science, a science of forms which have not hitherto been generally recognised as such, and the activities within and around them. The educational value of geography is as much in its scientific discipline as in its appeal to the imagination and sympathy. Prof. Gregory's books fall short of the ideal in so far as he excludes scientific geography from his descriptive pages. He has not yet recognised these higher groupings of phenomena connected by a specific topography. We venture to think that the first part of the twentieth century will be as noted for the recognition and study of these macro-organisms as the latter part of the nineteenth century was for the recognition and study of micro-organisms, and we believe that the beneficial effect on the body politic will be as great in the one case as it has been in the case of the individual in the other.

A. J. HERBErtson.

time in the subject of liquid fuel and the part it is likely to play in the future, Mr. Booth's book comes as a welcome record of the work done in the past, and would have been enormously enhanced in value had the references to the original papers been fully quoted. The first part of the work deals with the general properties and advantages of liquid fuel, and a good deal of this portion of the book might with advantage be omitted in a future edition, as, for instance, the chapter on water, its properties and purification, which are certainly out of place in a book devoted to a special subject and not likely to be used as a manual for boiler practice.

Mr. Booth's ideas on the subject of combustion are in the preferential combustion of the hydrogen in open to criticism, as he is evidently a strong believer hydrocarbons being the cause of the liberation of carbon

in the form of smoke and soot when there is insufficient air for complete combustion in the boiler furnace, but a consideration of the actions taking place in a if at such temperatures any preferential action exists, water gas generator may shake his belief in this, as, the fact that steam passed through red-hot carbon yields carbon monoxide, carbon dioxide, and hydrogen the element most favoured by the attentions of the would certainly point to carbon and not hydrogen as oxygen at the temperature of the furnace. On p. 105 the author breaks into amusing diatribes against the man of science, and comes to the conclusion that "when the most important industrial operations are absolutely neglected by our supposed teachers and leaders of scientific practice, it devolves upon those to whom science is less familiar, but more attractive, to step into the breach." This sentence probably explains a good deal of the vagueness to be found in the author's speculations on liquid and gaseous carbon and solid hydrogen in the portion of the work devoted to calorific value and combustion.

In the second part of the book practical engineering questions are dealt with, such as oil storage, the atomising of oil for combustion, and the work which has been done with liquid fuel, both on the Continent and in America, and here the author is thoroughly at home.

The engineering side of the question is admirably handled, and the collection of data which is given will render this part of the work of exceptional value to those dealing with this important subject.

The chapters on compressed air, flue gas analysis, and calorimeters will be welcome to many practical men, and the appendix is of special value as containing a report of the United States Naval Bureau on tests of liquid fuel for naval purposes.

There is no question that the time has now been reached when the methods of burning liquid fuel are

sufficiently advanced to ensure a very considerable advantage over solid fuel, and that the great point that remains to be solved is the oil supply, which at the present time is so completely in the hands of big commercial combinations that any development of its use at once leads to an increase in price that renders its employment impossible. It must also be clearly borne in mind that the total oil production of the world is but a small fraction of that which would be needed if liquid fuel became universally adopted, and that of this quantity only a small proportion would be of the quality fitted for fuel purposes on board ship.

Mr. Booth's book is one which will be welcomed by all interested in this very important subject.

OUR BOOK SHELF.

Die "Seele" als elementarer Naturfaktor. Studien über die Bewegungen der Organismen. By Hans Driesch. Pp. vi+97. (Leipzig: Wilhelm Engelmann; London: Williams and Norgate, 1903.)

Price is. 9d.

THE relation of soul to body is sometimes formulated as a "parallelism," sometimes as "interaction," and difference of theory depends, as a rule, on differences of standpoint. There is, however, another point of view in some ways more promising; it deals primarily with the organism as a whole, and posits the problem, "How must we conceive organisms which present the phenomena of purposive action?" The position is promising, because it appears free from the presuppo sitions involved in the direct question, How is mind related to body? but it really has an equally ambiguous element, because it involves placing on one scale forms of life which cannot be shown to possess the required continuous gradation. None the less, the method is interesting, and this book is an interesting example of it.

First, the author argues that mechanical explanations of life are inadequate; they fail to account for complicated readjustments; they fail, above all, to account for reactions which are not simple reflex movements, but imply choice and trial of means. The criticism establishing this deals with the older theories of reflex action, instinct, and the "Zentrum." This “Zentrum,” in any sense in which it subserves merely mechanical combination, must be rejected; for it the author has to substitute some conception which admits of "free combination." This conception suffers rather from brevity of exposition, and is defined chiefly by negation; some points emerge clearly; the physical elements (nervo-cerebral system) are not themselves final, but an intermediary factor; there is over and above these the system of what the author calls psychoids, apparently gradated (Oberpsychoid, Unterpsychoid, &c.); the structural basis of, e.g., association does not contain in itself the regularity required, but is a means to it. In addition to the mechanical factors, autonomous factors are asserted; the factors" condition, but do not make experience; the gap which a physicochemical theory leaves is filled by the" Psychoid-Theorie " (p. 66).

outer

Ph.D.

Indians of the South-west. By George A. Dorsey, (Chicago: Passenger Department, Atchison, Topeka and Santa Fe Railway System.) IT is characteristic of American enterprise that the Passenger Department of the Atchison, Topeka and Santa Fe Railway System should issue a concise handbook on the Indians of the south-west by a distinguished field anthropologist. This most fascinating and important ethnological area has been investigated by many distinguished American ethnologists, whose results have appeared in various publications. The disjointed character of these memoirs, although they are often presented with a great thoroughness, has rendered it difficult for students, on this side of the Atlantic at least, to gain a clear conception of the various Indian groups, and of the significance of their complex rituals. The time is therefore ripe for a succinct presentation of the main facts already published concerning these peoples. Dr. G. A. Dorsey, of the Field Columbian Museum, Chicago, has travelled extensively in the south-west, and readers of NATURE have frequently been informed He is there ore eminently qualified to undertake the of his valuable contributions to American ethnology. task, and in the 223 pages of this book he has condensed a vast amount of trustworthy information regarding the daily life, industries, and religious cere

monial of the natives.

The following subjects are dealt with:-the tribes, linguistic stocks and industries of the south-west peoples; the Pueblos of the Upper and Lower Rio Grande; the homes of the ancients; Zuñi and the seven cities of Cibola; domestic life of the Hopi; Flute, Antelope, Snake, and other ceremonies; ancient home of the Hopi; the Navaho, the Apache; tribes of the Yuman and Piman stock, and the tribes of southeastern California. The book is illustrated with a profusion of beautiful and instructive illustrations, and a valuable bibliography is appended. Doubtless the publication of this book, of which 15,000 copies have been issued, will lead to the south-west becoming a popular resort for tourists.

This will rapidly hasten the Europeanising and vulgarising of the most picturesque and unspoilt of the existing pagan peoples of North America; indeed, traces of this decay are not already wanting. If this book succeeds in the purpose for which it was brought out, it will materially, though unintentionally, help Columbian culture in North America. to destroy the last surviving relic of advanced pre

The Butterflies and Moths of Europe. By W. F. Kirby, F.L.S., &c. Pp. lii+432. (London: Cassell and Co., Ltd., 1903.) Price 21s. net.

THIS book was originally published in 1882, and then comprised all the species that were included in the catalogue of Staudinger and Wocke (1871). The present volume brings the subject much more up to present knowledge, as it now contains descriptions of all the species of strictly European butterflies and larger moths enumerated in the great catalogue of Palearctic Lepidoptera published by Staudinger and Rebel in 1901. The few species found in Madeira and the Canary Islands, but not met with on the Continent of Europe, have also been included, so that the work will afford an excellent help to any entomological Continental tourist, or those who perforce escape the rigour of our winter months in the Atlantic islands. Mr. Kirby has also brought our knowledge of the larvæ of these species up to date by the description of those discovered since the publication of his previous volume.

The author has achieved considerable success in the difficult task of writing a popular guide without pro

ducing a non-scientific volume, which is embellished with fifty-four plates, fifty-three of which are coloured, and contains a full and useful introduction. With this, among the many other popular works on natural history recently published, we may look forward to a prospective time, when the general reading public, and lovers of animal life, will be sufficiently acquainted with the main aspects of general zoology as to enable them better to grasp the real import of the many conclusions and theories-philosophical and otherwisewhich have followed the great Darwinian conception. It may also be hoped that the narrative of life-histories of insects, now so frequently detailed and so easily consulted, may incite a further cultivation of economic entomology, a subject in which our American cousins still hold the field.

Grandeurs Géométriques. By J. Pionchon. Pp. 128. (Paris: Gauthier-Villars, 1903.) Price 3.50 francs. EXPERIENCE in the teaching of young engineers at Grenoble has induced Prof. Pionchon to undertake the task of publishing some seventy little volumes presenting in a clear outline the fundamental notions, theoretical and practical, which should form the basis for further study. The collection includes sections on mathematics, mechanics, physics, electricity, and economics, and the present volume is the fourth of the first section. It explains in an elementary way the nature of the different geometrical entities and the methods by which they are measured. There is no attempt to dip beneath the surface and introduce any of the philosophy of the subject, but some passages in smaller print give rather more advanced considerations and analytical formulæ without proof.

If the book stood alone it could perhaps be passed without comment, but the prospect of seventy others of the same kind compels a word of criticism.

It

must be admitted that the contents appear to be perfectly sound, but beyond this we have little praise to bestow. Whatever it contains of value ought to be in the notebook of every engineering student who has had the minimum necessary instruction in mathematics, and if it is not already there, the reading of this volume will only lead to that undesirable sort of knowledge which too often forms the main part of the mathematical equipment of engineers, and is unfortunately encouraged by some of their teachers. The appearance of the pages suggests that they are designed to compensate physical as well as intellectual myopia, and this emphasises the inanity of many of the propositions. The author must be singularly devoid of the sense of humour. R. W. H. T. H.

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.]

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Secondary Radiation produced by Radium Rays.

I LATELY had occasion to produce some radium radiographs of two partially overlapping pennies contained in paper envelope which was laid directly upon the photographic plate. A print from one of the results shows that the shadow of the upper coin is blurred and diminished where the rays pass through air from the edge of this coin to the plate, but that it is sharp and of the correct size where the rays pass to the plate through the lower coin. This seems to point to the production of a considerable secondary radiation by the rays in their passage through air. L. R. WILBERFORCE.

University of Liverpool, December 22.

An Interesting Yucca.

IT frequently happens that facts of much general interest are published in systematic monographs and other taxonomic works, and are in consequence overlooked by many of those to whom they would be most valuable. Turning over the pages of the revision of the Liliaceous group Yucceæ, published with superb illustrations in the 1902 report of the Missouri Botanical Garden, I came across some statements which seem to deserve wider circulation and comment. The whole of the work referred to, by Dr. Wm. Trelease, is exceptionally well worth reading on account of the extremely lucid presentation of the facts, but the statements which especially interested me are as follows:

The subgenus Chænoyucca contains thirteen species, some of which have the style green while others have it white. Yucca glauca is the very common narrow-leaved greenstyled species of Colorado and northern New Mexico, extending to South Dakota and central Kansas. The inflorescence is simple, or with an occasional branch. Yucca constricta is a white-styled species, very similar to F. glauca, found from the Pecos River region of Texas to Seward County, Kansas, where it meets the range of Y. glauca. It has the inflorescence rather amply branched at the top. A few years ago Mr. James Gurney, head gardener of the Missouri Botanical Garden, was struck with the variety of foliage and difference of vigour of growth" shown by the Yuccas of Seward County, Kansas, all being ostensibly Y. glauca. He collected a considerable number of these plants to show the differences, and they were transferred to the Missouri Garden, where some of them have bloomed. Among them was one which had practically the foliage of Y. glauca, but it produced "a rather ample long-pedunculate panicle of pure white flowers, with white styles,' which began to expand at the end of the flowering period of Y. glauca. This specimen was by no means to be separated from Y. constricta. Other specimens exhibited the normal flowers of Y. glauca, and still others had flowers like those of glauca, but with a conspicuously branched inflorescence. This last form agrees with the long-lost Yucca stricta of Sims, but is placed by Dr. Trelease as a variety of Y. glauca. In addition to these differences in the flowers, the foliage varied in breadth and flexibility.

No suggestion is made by the author that the phenomena described are the result of hybridisation, but it is well known that Yuccas are frequently crossed in cultivation, and Dr. Trelease presents an extended discussion of Yucca hybridisation in another part of his paper. In the case of the Seward County plants, we have an unexpected and great mutability developing locally in an ordinarily stable species of wide distribution; and is it not suggestive, to say the least, that this should occur just where the ranges of Y. glauca and Y. constricta overlap, and that the socalled stricta should have more or less intermediate characters taken as a whole, while the features taken separately are nevertheless pure? May this not be a case conforming with the Mendelian laws? In any event, it seems well worth consideration, for the mutability has to be explained somehow or other, that is to say, there must be a reason for it.

Granting the supposed hybrid origin of Y. stricta, the case is curiously parallel to that of the perplexing woodpeckers of the genus Colaptes inhabiting the same region, which are intermediate between the eastern yellow-shafted and western red-shafted species.

The only other Yucca which could be involved in the above discussion is the green-styled Yucca mollis (Y. angustifolia mollis, Engelmann, 1873),' but this is not known to extend so far west as to meet the range of Y. glauca.

T. D. A. COCKERELL.

Colorado Springs, Colorado, U.S.A., December 13.

1 Dr. Trelease names this Y. arkansana, “in deference to the prevalent American practice in nomenclature." whereby mollis is held untenable because of Carrière's prior Y. gloriosa mollis. applied to a garden form. A practice which permits a name proposed for a garden variety of a different species to stand in the way of an otherwise valid specific name should urely be condemned.

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SOKOTRA.1

LTHOUGH the island of Sokotra is often seen by passengers on the great ocean steamers which pass by the Sokotran Archipelago on their voyages to and from India, eastern Asia and Australia, the fauna had been very imperfectly investigated when, in 1898, a party was dispatched by the joint exertions of the British and Liverpool Museums for the purpose of collecting specimens of the animals, vertebrate and invertebrate. The botany of Sokotra itself had been previously studied by Prof. Bayley Balfour and by Dr. Schweinfurth in 1879-81, and some collections of the animals Occurring had been made by them and by other visitors to the islands, but the zoology was still incompletely known.

The party of 1898 consisted of Dr. H. O. Forbes himself, Mr. W. R. Ogilvie Grant, of the British Museum, and a taxidermist. Native assistants and servants were engaged at Aden, and valuable aid was given by the Government of India, which supplied means of transport between Aden and the islands, and lent camp equipage for the use of the explorers.

The Sokotran Archipelago consists of (1) the large island of Sokotra, about eighty-five miles in length, lying 150 miles to the eastward of Cape Gardafui in Africa and about 230 miles S.E. of Ras Fartak in Arabia; (2) Abdel-Kuri, a much smaller island, lying about half way between Sokotra and Cape Gardafui; and (3 and 4) two islets, Semha and Darsi or Darzi, known as the Brothers, between Abd-el-Kuri and Sokotra. The two larger islands are separated by a submarine valley, 100 fathoms deep, whilst a channel several hundreds of fathoms in depth intervenes between Abd-el-Kuri and Cape Gardafui, and the sea between the islands and the Arabian coast is still deeper.

Dr. Forbes's party landed and made collections on Abd-el-Kuri, and they spent about two months in the hilly region of eastern Sokotra, but were unable to visit the smaller islets. The expedition was much delayed, first by some trivial political difficulties with the Sultan of Sokotra, and secondly, and more seriously, by severe attacks of

fever.

posal, and was able to visit the islet of Semha as well as Sokotra and Abd-el-Kuri. Amongst the members of the Austrian party were Prof. Müller, Dr. Kossmat the geologist, and Prof. Simony the naturalist. At a time when Dr. Forbes's party was suffering severely from fever, and had almost been brought to a standstill by illness, most valuable medical assistance was given to them by the Austrians.

The finely illustrated volume now published contains the results of the expedition, and owes its appearance to the Museums Committee of the Corporation of

Simultaneously with Dr. Forbes's expedition, an Austrian scientific party which, under the direction of Count Lambert, was engaged in exploring the archæology, geology, and natural history of southern Arabia, visited the Sokotran Islands. This party was larger and better equipped than Dr. Forbes's modest expedition, it had a steam vessel, the Gottfried, at its dis

"The Natural History of Sokotra and Abd-el-Kuri." Edited by

Henry O. Forbes, LL.D., Director of the Liverpool Museums, &c. Pp. xlvii+598; 30 plates and numerous figures in the text. (Liverpool: The Free Public Museums; Hy. Young and Sons; London: R. H. Porter.)

Liverpool, which has provided the funds, and authorised the publication of the work as a special bulletin of the Liverpool Museums. The book is edited by Dr. Forbes, and comprises a narrative of the journey from his pen, and descriptions by various naturalists of the different groups of animals, vertebrate and invertebrate, collected by the expedition. The list of authors is too long to quote in full, but it comprises, besides Dr. Forbes and Mr. Grant, several eminent zoologists, amongst whom are lenger, Mr. E. A. Smith, Mr. R. I. Pocock, Sir G. Hampson, and Mr. W. F. Kirby, of the British Museum staff, besides Colonel Godwin Austen, Mr.

Mr. Bou

McLachlan, Lord Walsingham, and several others. A complete list of the plants of Sokotra and Abd-el-Kuri, inclusive of important additions obtained by Dr. Forbes, is furnished by Prof. Bayley Balfour, whilst a note by Prof. J. W. Gregory on the geology is a reprint of a short paper published in the Geological Magazine for 1899. This paper, which was founded on a collection of rock specimens brought back by Dr. Forbes's expedition, is supplemented by an extract from a report by Prof. Bonney on a similar collection made by Prof. Bayley Balfour in 1880. It is very much to be regretted that a translation of some of Dr. Kossmat's published notes on the geology was not also added, for whilst, as might be expected in reports on rock specimens collected by naturalists who are not geologists, the notes now reprinted give a fair account of the crystalline and volcanic rocks of the Sokotran

Gregory in Australia is probably the reason why a fuller account of the geology as now known is not supplied.

The work is well illustrated with coloured plates and figures in the text. Amongst the plates, the representations of the wild ass (introduced by man but now feral), of some of the birds (especially a new goatsucker, Caprimulgus Jonesi), and of the land mollusca, spiders and insects (butterflies, moths, microlepidoptera, wasps and bees, beetles, &c.), are good examples of chromolithography. The text figures of mollusca and beetles, each surrounded by a grey rectangular area in which the actual shell or insect does not always occupy the central position, though good representations, have a somewhat unpleasing effect. The few figures of plants are good, and especial attention may be directed to the remarkable Euphorbia discovered by Dr. Forbes in Abd-el-Kuri.

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group, they afford a very imperfect idea of the sedimentary formations, although the latter occupy by far the greater portion of the islands. The massive Nummulitic, Alveolina, and Hippuritic limestones, of which the islands chiefly consist, and which are of much greater geological importance than the granitic formations underlying them, are only mentioned vaguely as Cretaceous and Eocene limestones. notice naturally is taken of one curious discrepancy between the collected specimens and Dr. Kossmat's statements. Both Prof. Balfour's and Dr. Forbes's collections from Sokotra contained comparatively modern volcanic rocks resembling those of Aden, whilst Dr. Kossmat states that no such rocks occur in Sokotra. ("Jungvulcanische Bildungen fehlen auf Sokotra-ganz im gegensatze zur gegenüberliegenden Küste Arabiens-vollständing," Sitz. math. nat. Cl. K Akad. Wiss. Wien, 1899, p. 77.) The absence of Prof.

As is usually the case in books like that now before us, some curious illustrations of zoological nomenclature are conspicuous. For instance, Mr. Kirkaldy, to whom we are indebted for an account of the Rhynchota, has invented a generic name which he spells Klinophilos. Naturalists in general who follow the old rules of Latin orthography would have written Clinophilus, but orthographical heterodoxy is by no means the most extraordinary feature of the case, for the new name is given to a genus the type of which appears, according to the rules of Linnæus himself, to be also the type of the Linnæan genus Cimex.

Again, in the two sections dealing with the land mollusca, each of the two authors quotes a generic name, Achatinelloides, given, not by themselves, but by another writer. It is difficult to understand why so absurd a term as this, derived from a double Latin diminutive of dubious accuracy by the addition of a Greek adjectival termination, should be preserved instead of being simply ignored. Some explanation, too, might have been vouchsafed why the same families of mollusca are termed Pomatiidæ and Pupidæ by one author, Cyclostomidæ and Helicidæ by the other.

The discussion of the "distribution of land and water in the Indian Ocean as indicated by a study of the fauna and flora of the islands" is one of the subjects mentioned in the preface as having been left over for a future publication. It is to be regretted that a general summary of the results obtained, so as to afford an idea of the zoological relations between Sokotra and the neighbouring continents, has not been added to the present volume, and it must be hoped that Dr. Forbes, who has already contributed to our knowledge of the distribution of animal life in the islands of the Indian Ocean, will before long publish his views on the results of his investigation of the Sokotran fauna.

The principal features of Sokotran zoology are the following. There are, as already remarked, no indigenous mammals, no batrachians or freshwater fishes. Amongst sixty-seven species of birds recorded from Sokotra, eleven appear to be peculiar to the island, and of the twenty-two birds from Abd-el-Kuri three are unknown elsewhere. Of twenty Sokotran land reptiles no less than fifteen are peculiar, and three genera out of thirteen; the number known from Abd-el-Kuri is only three, of which two are peculiar to the island, whilst one is rather widely dis