May 24, 1906] 



NATURE 



79 



which surround us are due 10 the interanion of 

 somethintf material and soniethinij spiritual, or (to 

 express it otherwise) to the fact that something 

 >piritual uses the material as its instrument or organ. 

 This seems to imply a dualism, but he also holds it 

 possible that " there may be some intimate and 

 necessary connection between a generalised form of 

 matter ,ind some lofty variety of mind." 



The arrangement of the various topics is not always 

 the best possible. This is partly caused by the in- 

 clusion of reprints from well-known journals — a prac- 

 tice which is open to criticism. But apart from these 

 slight defects the book deserves hearty commend- 

 .ition. 



The Fox. By T. F. Dale. (Fur, Feather, and Fin 

 .Series.) Pp. xiii + 238 ; illustrated. (London :Long- 

 mans. Green and Co., 1906.) Price 5^. 

 "The fox," writes the author in his opening para- 

 graph, " is at homo in Europe, Asia, including Indi.i, 

 .1 great part of Africa, the whole of North America, 

 and a distinct but allied species, Canis virginianus — 

 known as the grey fox in the United States — is found 

 In South .\merica." If he had tried to compress as 

 many errors as possible into a single sentence, he 

 cnuld scarcely have succeeded better. The fox is un- 

 known in India proper, it inhabits only the northern 

 fringe of .Africa, and the grey fox (L'rocyon cinereo- 

 iirijcnteiii) is a native of North and not of South 

 America. This is one of those numerous instances 

 u here authors of works on popular natural history 

 will go out of their way to refer to subjects which they 

 d) not understand, and whicli do not concern them. 

 H.-id Mr. Dale kept within his proper limits, we should 

 have had nothing but commendation to bestow upon 

 his work, in which the fox is discussed from the point 

 of view of the sportsman and the farmer in a very 

 thorough manner. The eight illustrations by Messrs. 

 Thorburn and Giles are all that can be desired, 

 although one of them follows somewhat closely on 

 the lines of a well-known sketch by the late Mr. Wolf. 



R. L. 

 Oologia universalis palcearctica. By Georg Kause. 

 Part i. (Stuttgart: Fritz Lehmann, Verlag ; 

 London : Williams and Norgate.) 

 Tins is the first part of a beautiful egg book, printed 

 entirely on separate sheets of cardboard, two sheets 

 being devoted to each species — one of coloured figures 

 of the eggs, the other of letterpress, backed with 

 references to the specimens figured. The text is in 

 German and English, and comprises a large number 

 of synonyms and local names, and a short description 

 of the range of the bird, its breeding habits, nest, eggs, 

 &c. The four species treated of in the first part are 

 the golden eagle, quail, song thrush, and raven, as 

 many as sixteen (odd) eggs of the last-named bird 

 (from different localities) being figured. In the case 

 of the song thrush we have five " clutches," and in 

 th.it of the golden eagle a clutch of two eggs and 

 three single ones. The colour printing has been very 

 successful, and admirers of eggs will w-elcome the 

 excellent selection of varieties which has been figured, 

 of each of which the " data " are given. We cannot 

 extend the same praise to the English version of the 

 letterpress, which is crude, too literal, and disfigured 

 by imfamiliar words and expressions. However, it is 

 possible to understand what is meant, although the 

 remark on the quail that " the Q only breeds, the male 

 is polygamons," reads strangely until we substitute 

 broods for breeds and correct the misprint. 



The work is to be complete in 150 parts, and Messrs. 

 Williams and Norgate point out that on the publica- 

 tion of Part ii. the price per part will be raised from 

 fifteen to eighteen pence. 



NO. 1908, VOL. 74] 



LETTERS TO THE EDITOR. 



[The Editor does not hold hitnself 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 Satvue. 

 No notice is tahen of anonymous communications.] 



Osmotic Pressure. 



In the concluding sentence of his most interesting letter 

 on this subject in your issue of May 17 (p. 54) Mr. 

 Whetham states that " The theory of ionic dissociation 

 rests upon electrical evidence, and by such evidence it must 

 be tried." It is unnecessary to dwell on the importance 

 of the pronouncement. 



Will Mr. Whetham kindly tell us how we kno7u all the 

 things which — in the final paragraph of his letter — he so 

 confidently asserts that we know ; in fact, what precisely 

 the electrical evidence is upon which the theory of ionic 

 dissociation now rests. He is a recognised master of lucid 

 exposition and will be able, I am sure, as counsel of the 

 whilom advocates of the doctrine of molecular suicide in 

 solution, to state the case fully and fairly on their behalf. 

 When we have this statement it will perhaps be possible 

 to consider the validity of his modest contention and 

 whether electricians alone have the right to pronounce 

 judgment. A plaintiff is usually sure of his case before his 

 cross-examination takes place. 



This request is preferred in no adverse i(r)onical spirit, 

 simply because I feel that it really is necessary that we 

 should be informed where we are exactly. Our friends the 

 ionic dissociationists are incorrigible squatters and seem to 

 think that they have acquired ihe right of preemption over 

 their adversaries' property ; it is difficult to know, a? they 

 object to stock-taking, whether they have given anything 

 in exchange for that they have lifted and what they have 

 jettisoned of their original property ; and until the elec- 

 tricians' title-deeds are shown and submitted to careful 

 scrutiny, chemists can scarcely be expected to admit that 

 thev are ousted from possession. 



As a chemist and a friend of the poor molecules, I fee! 

 that the aspersion of immorality should not be allowed to 

 rest upon them for ever unless the evidence be really con- 

 demnatory beyond question. In any case, it is important 

 that we should discover the true nature of the crime corn- 

 mitted in solution; to cloak the inquiry by restricting it 

 to thermodynamic reasoning — a favourite manceuvre of the 

 mathematically minded— is akin to using court influence 

 in abrogation" of full and complete investigation ; such a 

 course mav satisfy the physicist but is repulsive to the 

 chemist, who, although able, perhaps, to imagine the exist- 

 ence of a frictionless piston, yet desires, in the first place, 

 to get nearer to a knowledge of what happens to the real 

 tangible piston of practice. Henry E. Armstrong. 



Mr. Wheth.«i's letter in Nature of May 17 (p. 54) 

 raises clearly the whole question of the applicability of 

 thermodynamic reasoning to osmotic phenomena. As my 

 views as to the value of thermodynamic reasoning appear 

 to be somewhat heterodox, may I indicate some criticisms 

 of his remarks? 



All thermodynamic proofs assume the truth of the 

 " second law." Now the machinations of Maxwell's demon 

 have shown clearly that the meaning of this law, when 

 interpreted in terms of the molecular theory, is merely that, 

 in the processes considered, no differential treatment is 

 applied to the molecules in virtue of their different velocities. 

 The law mav or mav not be true in any particular case. 

 It cannot be'said that there is any a priori support for it, 

 or that a proof of its validity for one small branch of 

 phenomena would justify its application to a totally different 

 branch. 



In all treatises with which I am acquainted, when the 

 law has been stated, the only reasons alleged for believing 

 it to be true are those derived from our inability to construct 

 a heat engine which will work without equalising tempera- 

 ture. .\ few pages, before or after, will be found the state- 

 ment that we cannot construct a reversible heat engine: 

 but it is not pointed out that the irreversibility of all actual 

 engines would mask the effect of a violation of the second 

 law, unless that violation were very complete and the separ- 



