146 



NA TURE 



[December 16, 1897 



and hypotheses of the now largely-developed province 

 of electro-chemistry. 



The preface of the new edition contains a special 

 reference to the author's views concerning solutions — 

 a subject for which he expresses great personal predi- 

 lection, and to the experimental investigation of which 

 he has devoted some time and labour. A paper by 

 Mendeleefif relating to solutions of alcohol in water was 

 communicated to the Chemical Society of London in 

 1887. He now states that we have not yet " the right to 

 consider even the most elementary questions respecting 

 solutions as solved." " My own view is that a solution 

 is a homogeneous liquid system of unstable dissociating 

 compounds of the solvent with the substance dissolved." 

 In a foot-note, beginning p. 64, he explains the gas theory 

 as applied to dilute solutions, and expresses the view 

 that the physical and chemical aspects of the question, 

 referring respectively to dilute and strong solutions, must 

 be reconciled. The passage is too long for quotation ; 

 but supporters of the so-called hydrate theory may still 

 count the great Russian chemist as on their side, at any 

 rate so far as strong solutions are concerned. 



There are, of course, many other subjects which the 

 reader of the book will pursue with much interest, in 

 view of the eminence of the author and the originality 

 with which they are treated ; but none of these will equal 

 in attractiveness the subject of the grouping of the ele- 

 ments and the development of the periodic law. It is 

 interesting to remember that, as the author tells us in 

 the preface (p. xii), it was while engaged in writing the 

 first edition of the book in 1869 that he first perceived 

 the scheme and the application of the periodic law in 

 its entirety. But it is only at the opening of the second 

 volume that we come to the exposition of the principles 

 which guided him in the grouping of the elements. This 

 is accompanied by a foot-note which contains a historical 

 rhuine of the course of events which led ultimately to 

 the recognition of these important principles by all 

 chemists. And here we find a passage {7iote 13, p. 26) 

 which sets forth clearly the depth and solidity of Men- 

 deleeff's conception of the periodic " law," and the 

 superiority of his claim to be regarded as the discoverer 

 of the relation of properties to atomic weight among the 

 elements. Having become convinced that the atomic 

 weights and properties of the elements were mutually 

 related in a certain manner, the Russian chemist did not 

 hesitate to alter accepted atomic weights when required 

 to fall in with the scheme, and to predict the properties 

 of then undiscovered elements ; while " neither De 

 Chancourtois, to whom the French ascribe the discovery 

 of the periodic law, nor Newlands, who is put forward 

 by the English, nor L. Meyer, who is now cited by many 

 as its founder, ventured to " do anything of the sort. 



As such fortunate and valuable consequences have 

 happily followed the study of the atomic weights by 

 Mendeleefif, it is perhaps hypercritical to complain of his 

 use of the term "law" in the vulgar ambiguous sense. 



What after all is a "law of nature " ? Is it not a com- 

 pendium or summary of a series of observed agree- 

 ments ? and the statement so often used by Mendeleefif, 

 that "the laws of nature admit of no exception," by 

 no means proves that exceptions to any and every 

 recognised law of nature may not hereafter be discovered. 

 NO. 1468. VOL. 57] 



As such a statement now stands, it merely implies • that 

 in most cases the induction is at present incomplete. 

 The question now comes, whether the periodic law 

 itself is a " law of nature " ? This is a question which 

 must be troubling very much the discoverer of the law 

 at the present tinre, now that the individuality of argon 

 and, though less certainly, that of helium have been 

 established. The subject is dealt with in Appendix iii. 

 at the end of the second volume, written by Prof. 

 Mendeleefif in February 1895, and here he clings to the 

 idea that argon is a polymeride of nitrogen, or N3. 



This hypothesis, however, cannot be maintained. All 

 that is known of argon shows that it is a gas having a 

 density lower than 20 (H = I ), and hence that its molecular 

 weight is less than 40, while that of N3 would be 42. 

 Argon and helium can at present be regarded only as a 

 kind of chemical monsters brought unexpected and un- 

 welcome, like the cuckoo, into the previously happy 

 family of the elements where no place is provided for 

 them. What, then, becomes of the " law of nature " if 

 these two substances are admitted to be exceptions to 

 the law as it now stands ? and yet that they are exceptions 

 is the conclusion which seems inevitable. W. A. T. 



THE NATURAL HISTORY OF THE ANCIENT 

 WORLD. 



Les Choses Naturelles dans Homcre. Par le Dr. A. Kums. 

 Pp. 194. (Antwerp : Buschmann. Paris : Alcan, 1897.) 



Gleanings from the Natural History of the Ancients. 

 By the Rev. M. G. Watkms, M.A. Pp. xiii + 258. 

 (London : Elliot Stock, 1896.). 



77/^? Works of Xetiophon. Translated by H. G. Dakyns, 

 M.A. VoL iii. part ii. Pp. Ixx -I- 130. (London : Mac- 

 millan and Co., Ltd., 1897.) 



Aristotle on Youth and Old Age, Life a7id Death and 

 Respiration. Translated, with Introduction and Notes, 

 by W. Ogle, M.A., M.D. Pp. 135. (London : Long- 

 mans and Co., 1897.) 



THE consideration of the animal world is usually 

 approached from one or other of three points of 

 view. We may be interested in the structure — the 

 morphology and physiology — of animals, and in their 

 place in nature : this is the biological interest. Or we 

 may be especially interested in their habits and doings, 

 and every one has at least observed something of the 

 characters and ways of more than one species of animal. 

 Or we may regard animals as objects of the chase or 

 material for human food. The first of these interests is 

 purely scientific ; it must exclude hearsay and fancy ; it 

 must be based on the most careful observation and ex- 

 amination with the aid of all the appliances that con- 

 temporary art and manufacture can furnish ; and it must 

 admit nothing that is unverifiable or supported by doubtful 

 authority. On the other hand, the study of the habits 

 and characters of animals can seldom confine itself to 

 lines so rigidly laid down as these ; not only is it extremely 

 difficult for the most scientific investigators to interpret 

 or even to record the actions of the lower creatures with- 

 out a certain, often unconscious, anthropomorphism or 

 reading-in of motives into them ; but we are also con- 

 fronted by a mass of current beliefs and superstitions, 

 and imperfectly authenticated tales which, in view of their 

 frequent repetition and the widespread evidence accorded 



