182 



KNOWLEDGE. 



[August 1, 1900. 



by some eighty-three clear and instructive illustrations, while the 

 bibliography at the end of the volume, occupying as it does over 

 forty pages, will prove of real service to students of bacteriology 

 and to the scientific brewer. 



"The Principles of Mechanics." By Heinrich Hertz, translated 

 by D. E. Jones, E.so. (Macmillan.) " 10s. net. "Presented in a 

 new form " is the claim jjut forward in this treatise on the principles 

 of mechanics. In it the axithor has endeavoured to give a consistent 

 representation of a complete and connected system of mechanics, 

 and to deduce all the separate special laws of this science from a single 

 fundamental law which, logically considered, can, of course, only 

 be regarded as a plausible hypothesis. He has chosen as his starting- 

 point that of the oldest theories, namely, the conception that all 

 mechanical processes go on as if the connections between the various 

 parts whch act upon each other M'ere fixed, a method of procedure 

 in which much scientific insight and imaginative power are re- 

 quired, and, with all its im|ierfections, the logical .system of 

 dynamics thus evolved with the greatest ingenuity and perfect 

 mathematical form will be appreciated as a guide to the general 

 characteristics of natural forces. It is a work unsuited for the 

 systematic teaching of mechanics, in spite of the fact that it affords 

 a comjjlete survey of all the more important general propositions in 

 mechanics. All the 2>rinciples are there, it is true, just as the 

 chemical composition of water is the .same at the Poles and the 

 Kquator, but to bathe in the Arctic Ocean one needs hardening a 

 little, and to read this book with profit it is necessary to approach 

 it through a milder medium. 



"Practical Physiology." 7th Edition. By M. Foster and J. N. 

 Langley. (Macmillan.) Illustrated. 7s. 6d. Sir Michael Foster's 

 book, first printed in 1876. and now having reached the 7th edition 

 under the care of Drs. Langley and Shore, needs but a, few words of 

 e.\planation as to the modifications introduced in order to meet the 

 present day requirements. While the original general arrangement 

 remains practically the same, the sections dealing with chemical 

 physiology and the physiology of muscle and nerve have been ex- 

 tensively revised, and we note with some regret that the portion on 

 the dissection of the rabbit and dog has been omitted, because, as 

 the authors say, " the specialization of study which has taken p ace 

 in the last twenty-five years seemed to make this omission in- 

 evitable." Still, in our opinion, the book in its amended form will 

 maintain a foremost place among laboratory manuals of its kind. 



"Man and His Ancestor." By Charles Morris, vii. and 238 pp. 

 (New York : The Macmillan Company.) 5s. Towards the end of 

 his book Mr. Morris describes its purpose as being " to trace the 

 evolutionary origin of man, in his ascent from the lower animal 

 world to his full stature as the physical and intellectual monarch of 

 the kingdom of life" (p. 225). We had come to the conclusion, 

 before reaching his concluding chapter, that Mr. Morris had suc- 

 ceeded in giving, in a very attractive manner, a fair exposition of 

 the present state of evolutionary ideas on the ancestry of man, so 

 that we are able to congratulate him upon having satisfactorily' 

 completed the task he set himself. Starting with a rapid review 

 of the vestigial structures found in the human body. Mr. Morris 

 proceeds to detail the various relics of ancient men which have tieen 

 discovered in different localities. The questions of the transition 

 from quadruped to biped and the steps which led to a completa 

 freedom of the arms are then dealt with, after which less teclmical 

 subjects are considered, such as, the development of intelligence, 

 the origin of language, the evolution of morality, and man's relation 

 with things sjiiritual. We surmise that tlie majority of people 

 who study books of this class are more directly interested in the 

 theory of evolution so far as it takes notice of the moral side of 

 man's personality, and they will be most anxious to know how this 

 subject is handled. One or two sentences will .serve sufficiently to 

 indicate the author's view. " What we call sinfulness is largelv a 

 matter of custom and convention. Men cannot properly be said to 

 sin when their actions are checked by no conscientious scruples, and 

 what one people woidd consider atrocious instances of wrong-doin", 

 might be looked upon as innocent and even estimable by a people 

 with a different moral standard " (p. 221). Sometimes Mr. Morri.5 

 shows an unfortunate disposition to forget his scientific resolutions 

 and indulges in fanciful language, which is out of place in a serious 

 treatise, e.g., " Tlie love principle is the innate moral element of the 

 universe. Its rudimentary form is the attractiim between atoms, 

 which expands into the attraction between spheres. We see a 

 development of it in the magnetic and electric attractions, and a 

 higuer one in the sexual attraction that exists in the lowest or- 

 ganisms. Its expansion continues until it reaches the high level 

 of human love and social sympathy" (p. 217). 



There is now in the press, and will shortly be published by 

 Messrs. Young in Liverpool, and Messrs. Porter in London, the 

 Beport on the conjoint expedition to Sokotra and Abd-el-Kuri, 

 conducted in 1898-9 by the British Museum (represented by Mr. 

 Ogilvie-rTrant. of the Zoological Dcjiartment) and the Liveriwol 



Museums (represented by the Birector of Museums to the Cor- 

 poration, H. O. Forbes, ll.d.). The expense of its publication 

 is borne by the Museums Committee of the Liverpool City 

 Council, and it is edited by Dr. Forbes. It will be illustrated by 

 between twenty-five and thirty plates, chiefly coloured, depicting 

 the zoological and botanical discoveries of the expedition, the 

 ethnography of the islands, etc. The introductory chapters by 

 the Editor give an interesting account, fully illustrated in the text, 

 of the journey, of the islands, and of their inhabitants. The scien- 

 tific chapters are contributed by Lord Walsingham, f.r.s., Prof. 

 Balfour, r.K.s.. Mr. Boulgcr. r.B.s., Br. Forbes, Mr. Ogilvie 

 Grant, Mr. A. E. Smith, Col. Godwin-Austin, f.r.s., Mr. De 

 Winton, Sir G. Hamjison, Bart., Mr. K. I. Pocock, and other 

 well-known naturalists. 



BOOKS RECEIVED. 



A Ouide to Chamounix and the Range of Mont Blanc. By Ed 

 Whymper. (Murray.) 3s. net. 



A Guide to Zermatt and the Matterhortt. By Ed. Whymper. 

 (Murray.) 3s. net. 



The Year Booh of Photographi/ and Amatews' Ouide, 1000. 

 (Fhotographic Neir.i Office.) Is. net. 



A Elifory of Decoratii'e Art. By W. "N. Brown. (Scott, Green- 

 wood & Co.) L's. (id. net. 



The Fifth and Si.vth Books of Euclid. By M. J. M. Hill. 

 (Camb. L^niv. Press.) (is. net. 



Ad Astra. By Charles Whitworth Wynne. (Grant Richards.) 

 7s. 6d. net. 



The Philosophy of Many Things. By Mary Leicester. (Lloyd.) 



Text-Book of Zoology. Fart I. — Mammals. By Br. Otto Schenieil. 

 Edited by J. T. Cunningham, M.A. (Black.) Illustrated. 3s. tid. 



First Stage Botany. By Alfred J. Ewart, D.sc (Olive ) 2s. 



Larengro : The Scholar, the Gipsy, the Priest. By George 

 Borrow. Minerva Library, (^\'ard. Lock.) 2s. 



Flesh Foods. By C. Ainsworth .Mitchell. (Griilin.) lOs. 6d. 



Foundations of Analytical Chemistry. By Wilhelm Ostwald. 

 Traii-lated by George M'Gowau. (Macmillan) 68. net. 



Functions of Squares. By M. A. McGinnis. (Sonnenscheiu ) 5s. 



Eesults of Bain, Siver, and Evaporation Observations made in 

 N.S. Wales, ISHS. By H. C. Kussell, c.m.g., f.r.s. 



Domestic Science. By Thomas Cartwright, b.a. (Nelson.) 2s. 



Official Year-Book of the ScientiHc and Learned Societies, 1900. 

 (Griflin.) 7s. 6d. net. 



Introduction to Zoology. By Chas. B. Bavenport and Gertrude 

 Crotty Davenport. (Macmillan.) Gs. 



Eadiographic List ._ (Isenthal k, Co.) 



H cttcr s. 



[The Editors do not hold themselves responsible for the opinions 

 or statements of correspondents.] 



MENTAL^PEESPECTIVE. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — The discussion which has been occupying the 

 attention of the members of the British Astronomical 

 Association of late concerning the well-known, but none 

 the less curious, apparent enlargement of heavenly bodies 

 when seen near the horizon* has called forth several 

 ingenious theories to account for the phenomenon. That 

 this enlargement of the sun or moon when seen on the 

 horizon is purely illusory is acknowledged by all, so 

 tliat it is evident some kind of mental deception is here 

 at work which tends to falsify our estimates of distance 

 and consequently of magnitude. It has been suggested, 

 for instance, that, when looking at the moon near the 

 horizon, we arc unconsciously aided in our estimate of 

 its distance by reference to intervening laud-marks, such 

 as trees, hills, or houses, the distance of which we 

 already know, whereas, when looking upward at the 

 moon in the zenith, there is nothing whatever to guide 

 us. Now it has been observed that the distance of 

 objects is almost invariably under-estimated when we 

 are deprived of our usual land-marks, as, for instance, 

 at sea, and it is suggested that by analogy the distance 

 of objects in the zenith, or at high altitudes, is similarly 

 under-estimated. Thus, the moon, sub-tending, as it 



* Journal uf tlie Brit. Astio. Assoc, Vol. X., Nos. 1, 3, 4 and 5. 



