I50 



NATURE 



[June 18, 1903 



expected. The subject, however, is treated very con- 

 cisely and generally very clearly. There is rather a 

 want of lucidity, however, in his treatment of the syn- 

 thesis of indigo on p. 512. The chapter on the diazo- 

 compounds and the short resume of Hantzsch's work 

 in this direction are very good, and his remarks upon 

 the electro-reduction of nitro compounds are also 

 excellent. 



Prof. Holleman pays particular attention to the 

 physico-chemical side of the subject, an aspect which 

 has been neglected by most writers of books on organic 

 chemistry. On p. 188, for example, in the chapter 

 upon polybasic acids, he devotes a long paragraph to 

 their physical and chemical properties; again, on p. 

 196, he gives a clear explanation of the electro-synthesis 

 of dibasic and other acids, while on p. 334 he describes 

 Tafel's fine work on the electro-reduction of purine 

 derivatives. In fact, one of the chief values of the work 

 is the welding together of physical and organic 

 chemistry. 



The book is hardly suitable for beginners or for 

 students who want (we will not say require) just a 

 smattering of organic chemistry, but for the earnest 

 student of the subject the work is one which can be 

 most highly recommended. The style is good, the 

 method of arrangement is excellent, and we think that 

 there are few who will lay down the book after having 

 studied it and feel disappointed. 



Messrs. Wiley have produced the book in excellent 

 style, and have spaced out the formulae and equations 

 in a lavish manner. Truly science knows no nation- 

 ality — the book is written by a Hollander, translated 

 bv a Scotchman, and published by an American house. 



F. M. P. 



Education in Accordance with Natural Law. Sugges- 

 tions for the Consideration of Parents, Teachers, and 

 Social Reformers. By Charles B. Ingham. Pp. 

 xi+125. (London: Novello and Co., Ltd.; New 

 York : Novello, Ewer and Co., n.d.) Price 35. net. 

 Ever since the publication of Rousseau's " liimile," 

 with its well-known opening sentence, " Tout est bien 

 sortant des mains de I'Auteur des choses, tout 

 degenere entre les mains de I'homme, " there have been 

 writers reflecting more or less satisfactorily the 

 illuminating ray which Jean Jacques directed against 

 the educational formalism of his day. Of course, if 

 ■educational methods contravene the laws of nature, 

 good results cannot be expected ; but it is of supreme 

 importance that writers venturing to define and 

 formulate a system of education in conformity with 

 natural law should at least first make sure that they 

 understand the broad generalisations they call to 

 their aid. An examination of Mr. Ingham's argu- 

 ments gives rise to the suspicion that he has not com- 

 pletely mastered the conclusions at which men of 

 science have arrived, and that his acquaintance with 

 physical science is scarcely intimate. But Mr. Ingham 

 is an experienced teacher, and has many sensible 

 pieces of advice to offer, and even if the truths he 

 advances are not new, they certainly are not univer- 

 sally adopted yet. To mention a few points on which 

 the author has sound views is alone possible here. 

 He advocates earnestly the need for more scientific 

 methods in education ; he pleads for more leisure time 

 for boys and girls, in which they may follow their 

 own devices ; and he inveighs against the unsatis- 

 factory early training of girls. He has not, we think, 

 given science a sufficiently important place in the 

 education of young people, but there can be little 

 doubt that if parents could be persuaded to read the 

 book they would have q clearer idea of what the aim 

 of education should be. A. T. S. 



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 commutiications.] 



Psychophysical Interaction. 



I AM interested by the letter of the professor of philosophy 

 in the University of Birmingham on p. 126, and if your 

 readers are not weary of the discussion — as I see no reason 

 why they should be, since it is clearly a difficult question 

 which must be discussed from time to time as science 

 advances — ^.I should like to add a few words. 



When Prof. Muirhead says that my recent contention was 

 advocated by Descartes, he is stating what is of interest, 

 but what I did not know ; I was not aware that the idea 

 of energy, or even of momentum, was sufficiently clear in 

 his era. But however this may be, he must not think that 

 I regard the statement " that mind cannot produce energy " 

 as axiomatic. It is a question not of axiom, but of fact. 

 It seems to me that live things do not generate energy and 

 do direct it ; so I assert this, not as a necessity of thought, 

 nor as an idea for which I have a special predilection, but 

 simply as an experience. If Descartes maintained the same 

 thesis, so much the more likely is it to be true. 



Inert matter — all matter is inert — matter devoid of life then 

 let us say, moves (technically, is accelerated) when and be- 

 cause it is pushed from behind. Live matter moves or is im- 

 pelled to move from other motives ; it is urged by anticipa- 

 tion of the future sometimes, by gratification of appetite for 

 instance, ^ by avoidance of pain, often. A typical case i^ 

 a coster mcmger's vehicle propelled by a bunch of carrots, or 

 by the blows of a stick applied in indiscriminate profusion. 

 There is nothing like that in storm or cataract or tide ; nor 

 is there anything like it in motor-car or railway-train, 

 unless we include in the machinery the mind of the 

 engineer. 



Prof. Muirhead recommends a pacification of the question 

 in the ultimate nirvana of idealistic monism. I am dis- 

 posed to acquiesce ultimately in this destination, but I feel 

 that there is something more proximate to be attained first. 

 Philosophers go so fast and so far, they do not give the 

 scientific man a chance ; he wants to study the landscape 

 and grub by the roadside. The ultimate outlook is doubt- 

 less there, very fine and attractive, like the setting sun ; 

 but the traveller to the west has much to see and much 

 to do, and a constant gaze too far ahead may only dazzle 

 him and unfit him for his proper work on the terrestrial 

 sphere. Oliver Lodge. 



Oxford, June 12. 



The opponents are not getting into close quarters. Dr. 

 Hobson was irreproachable, but the others are using the 

 word " force " all through the discussion, although it is 

 the most unhappy word anyone could use in a controversy 

 about fundamental physical conceptions. Its object is to 

 enable us to contemplate one aspect of an action while we 

 dismiss the other absolutely from our minds, because, when 

 we want to give all our attention to one of the two bodies 

 concerned, it helps us to ignore the other as much as 

 possible. 



It is remarkable also that Prof. Minchin should write 

 that " guiding or deviating forces," if they allow the 

 universe to keep its total energy intact, " infallibly alter 

 its total momentum." Prof. Ward seems to have said the 

 same thing, and the curious error remains without specific 

 contradiction. Yet anyone who remembers that if there 

 are n particles in the universe, there are 3_w velocities for 

 a sprite to amuse himself by tinkering with, will agree 

 that he must, indeed, be a stupid or self-willed sprite who 

 could not arrange to keep 2;«w^ Swl, 5wj>, and 2mi un- 

 changed while he disported himself with variations of the 

 other 3« — 4 integrals. 



Though that is merely a mistake on a side issue, an 

 example on it will serve to put clearly the two different 

 points of view. Suppose that there are two bodies of equal 

 mass 2m moving due north with velocities of 9 and i 



NO. 1755, VOL. 68] 



