June 17, 1897] 



NATURE 



149 



" The hi7u of definite proportions affirms that when 

 two substances unite together to form a given compound 

 they can unite only in a fixed proportion ; . . ." 



'Why '■'■ two substances"'} What exactly is "/« a fixed 

 proportion " ? Why " they can unite " ? Would not a 

 student find much difficulty in understanding the con- 

 clusion that is drawn from the law of reciprocal pro- 

 portions ? This conclusion is 



" For each element, therefore, there is a fixed propor- 

 tion in which it enters into any state of chemical union." 



The laws of chemical combination cannot be under- 

 stood without the help of examples worked out fully from 

 the basis of analytical and synthetical data. I cannot 

 find in these pages any statement of the nature of the 

 evidence whereon these fundamental laws rest ; nor can 

 I discover any suggestion of the vast importance of these 

 generalised statements of facts — the laws of chemical 

 combination — which we have every reason to regard as 

 true natural laws. 



On p. 238 sixteen lines are devoted to the atomic 

 theory of Dalton. I am certain that no student could 

 obtain, from the author's statement of this theory, a clear 

 mental image of the Daltonian conception of the atom. 

 On this page occurs the statement 



"a group of atoms united together chemically is called 

 a molecule." 



And on p. 240, after the enunciation of the law of 

 Avogadro, we read 



" by a molecule is here understood a small portion of 

 the substance of the gas made up of atoms which do not 

 separate from one another during the movements of the 

 molecule." 



This is altogether insufficient. Reference is made, it 

 is true, to " Kinetic Theory, p. 239"; but no clear and 

 sufficiently detailed statement of what is to be understood 

 by the word molecule is to be found in the paragraphs 

 devoted to that theory. 



.■\s regards the methods employed for determining the 

 relative weights of molecules and the relative weights of 

 atoms, I do not think that a student of fair intelligence 

 and perseverance will be able to realise these methods as 

 definitely as they ought to be realised, even by a very 

 careful consideration of the paragraphs devoted to these 

 subjects on pp. 241 to 251. About 10 pp., 254 to 264, 

 are concerned with the very difficult subject of valency or 

 atomic value and the application thereof to constitutional 

 formulie. 



"... an atom of certain elements can replace or be 

 substituted for only one atom of hydrogen, whereas the 

 atoms of other elements can replace 2, 3, 4, &c., atoms of 

 hydrogen." 



Then follow reactions meant to illustrate this state- 

 ment. And then we read 



"This difference of combining or saturating power, 

 originally called atomicity^ now more appropriately called 

 valency, is sometimes denoted by placing dashes . . ." 



This is, in my opinion, slipshod and hazy writing, and 

 it cannot but induce to slipshod and hazy thinking. 



There is an extraordinary statement on pp. 255, 256 

 about t/te law of even numbers. This " law," we are told, 

 is that 



"... in all such compounds [saturated or normal 

 compounds] the sum of the perissad elements (that is, 



NO. 1442, VOL. 56] 



elements whose atoms are of uneven valency) is always 

 an even number." 



Take the case of the gaseous molecule NO. The sum 

 of the perissad elements, to use the author's loose phrase, 

 in this compound is not an even number. Perhaps this 

 compound is not a " saturated or normal compound " ? 

 Well, define what you mean by " saturated or normal," 

 and then show that the lata of even numbers is of any 

 value as an aid to accurate research and accurate 

 thinking. The existence of the three gaseous molecules 

 InCl, InClg, InCl.^ disposes of the law of even numbers, 

 if the la7a is anything more than a mere playing with 

 numbers. 



I have tried to get some clear notions about heat and 

 chemical affinity from the pages which deal with that 

 subject ; but 1 have failed. These pages give one a little 

 information about some portions of thermal chemistry ; 

 but the subject of chemical affinity is not really touched 

 on at all. 



On p. 287 there is a guarded, but still misleading, 

 statement which comes perilously near an enunciation of 

 'Rtrthtloi^?. law of maximum work, which "law" is both 

 false in fact and untrue in principle. 



To sum up the complaints I make against this book. 

 There is a want of proportion. There is a failure to 

 appreciate the relative importance of the various parts of 

 the science. There is a failure to describe facts of 

 observation as such, and then to show how hypotheses 

 arise and react on these facts, until a general theory is 

 attained, which illuminates the foundations whereon it 

 rests, and suggests the lines on which search must be 

 made for more facts. 



I admit the vast difficulty of writing an elementary 

 manual of chemistry. The past is strewn with failures, 

 to which I have myself contributed. I am exceedingly 

 sorry to say that, in my opinion, this book is not a 

 success. M. M. Pattison Muir. 



PHILOSOPHY AND PHILOSOPHERS. 



History of Philosophy. By Prof. A. Weber. Trans- 

 lated by Dr. F. Thilly. Pp. xi -1- 630. (London : 

 Longmans and Co., 1896.) 



System der Philosophie. Von W. Wundt. Zweite 

 umgearbeitete Auflage. Pp. xviii 4- 689. (Leipzig : 

 Engelmann, 1897.) 



FOR Prof. Weber the chief interest of his subject 

 obviously lies in the post Kantian schools, and his 

 own solution of the problem of philosophy, as shaped by 

 the influence of the conceptions and methods of the 

 natural sciences on the one hand, and by the e.xigencies 

 of ideal and optimist ethics on the other, is in the 

 direction of a " concrete spiritualism." The key-word 

 of this he finds in will or force rather than reason, but 

 a Wille sum Guten in place of Schopenhauer's will to 

 live. It is in virtue of his firm hold upon modern 

 problems that his review of the way in which they have 

 been historically evolved is so far successful that some, 

 at least, of the dry bones of the History of Philosophy 

 are made to live. Those writers whose antagonism to 

 a dualist metaphysic makes them forerunners of the 

 post- Kantian development— Bruno for example, and 



