NATURE 



[July 2. 1903 



for the modern experimental treatment of psychology, 

 and has the merit of having introduced these methods 

 in the University of Wales ; it is therefore regrettable 

 that he has not dwelt upon the value of psychology, so 

 treated, as a training in accurate observation. For no 

 other experimental science exercises so constantly, or 

 makes so exacting demands of, the faculty of close ob- 

 servation and the power of voluntary control of the 

 attention, the development of which two powers is, or 

 should be, a prime object of all educational efforts. 



W. McD. 

 Photography. Edited by Paul N. Hasluck. Pp. i6o. 



(London, Paris, New York, and Melbourne : 



Cassell and Co., Ltd., 1903.) Price is. 

 Hand Camera Photography. By Walter Kilbey. Pp. 



124. (London : Dawbarn and Ward, Ltd., 1903.) 



Price IS. net; cloth, 25. net. 

 These little books are both intended for beginners in 

 photography. The comprehensive title of the first is 

 reflected in the claim made in the preface that the 

 " Handbook contains, in a form convenient for every- 

 day use, a comprehensive digest of the knowledge of 

 photography, scattered over more than twenty 

 thousand columns of Work.'' Doubtless the volume 

 will be of value to readers of Work in saving many 

 a reference to its thousands of columns, and as it is 

 written chiefly by a professional photographer, others 

 will probably be interested in such chapters as that on 

 retouching. Much of the matter is too concise. It 

 is impossible, for example, to give useful directions 

 for the making of a 20 x 15 wet collodion negative in 

 less than one small page, including instructions as to 

 what to buy for the purpose. 



The second volume is of a different kind. It is 

 written by an amateur for amateurs, and the author 

 has proved by his published photographs that his ex- 

 periences are valuable. Of course, everyone will not 

 corroborate all the opinions expressed, for the book 

 has individuality and does not pretend to be a com- 

 prehensive treatise. It is essentially popular in style, 

 and meets several difficulties that trouble beginners, 

 and that many authors do not think of referring to. But 

 Mr. Kilbey has surely forgotten himself when he sug- 

 gests the use of a swing back in order to get such a 

 view as an abbey with a foreground of rushes more 

 easily into focus. Some ten pages further on an ex- 

 ample of distortion due to tilting the camera is illus- 

 trated. We fear that some w411 infer from these illus- 

 trations that tilting the camera gives distortion, while 

 swinging the plate does not. The book will be found 

 to be a very useful guide by those who use hand 

 cameras, and whose knowledge of photography is but 

 slight, while others who may rank with the author in 

 experience can hardly fail to find useful suggestions. 

 Mise en Valeur des Gites Mineraux. By F. Colomer. 



Pp. 184. (Paris : Gauthier-Villars, 1903.) Price 3 



francs. 

 Most of the French treatises on mining hitherto pub- 

 lished deal chiefly with the extraction of coal, and this 

 unpretentioi/j and inexpensive volume will therefore 

 undoubtedly prove useful to managers of metalliferous 

 mines. It gives a clear summary of modern practice 

 in metal mining. It is up-to-date and compact with 

 facts. The matter is divided into ten chapters, dealing 

 respectively with the definition of an ore-deposit, access 

 to the deposit, method of working, breaking ground, 

 rock-drills, explosives, transport, raising ore, drainage 

 and ventilation. The work concludes with a brief glos- 

 sary of technical terms. The absence of illustrations 

 renders some of the descriptions somewhat obscure. 

 The author has, however, carried out his task with 

 care and accuracy, and has produced a volume valuable 

 to the student desirous of becoming familiar with 

 French mining terms. 



NO. 1757, VOL 68] 



LETTERS 10 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 communications.] 



Psychophysical Interaction. 

 My authority for attributing to Descartes the distinction 

 between " creation " and " direction " is Leibniz's " Theo- 

 dic6e " (Erd. 519). I ought to have stated more clearly than 

 I did that he, of course, conceived of the problem in the form 

 in which it presented itself to his age as one of " motion " 

 rather than of energy and momentum. In referring to 

 the history of the discussion at all, I merely meant to 

 indicate its antiquity. This, of course, is no reason why 

 it should not be reopened now. Every generation of thinkers 

 has to adjust old solutions to new forms of a problem. It 

 is, however, a reason why we should inquire whether a 

 controversy of so long a standing may not be founded on a 

 radical misunderstanding. 



The object of my letter, if I may repeat it, was not to 

 advocate the removal of the discussion from the field of 

 fact to the nirvana of monistic idealism, as Sir Oliver 

 Lodge suggests, but the preparation of the way for a better 

 understanding between the combatants by inviting them, 

 experimentally, at least, to consider the facts from a different 

 point of view, or rather from the point of view of the most 

 fundamental of all facts, our own will and personality. In 

 making this suggestion, I expressly disavowed the intro- 

 duction of anything transcendental that might dazzle the 

 eyes or divert attention from the " landscape " or the 

 "wayside." The suggestion, on the contrary, was that 

 wayside facts might be better understood and unsatisfying 

 controversy avoided, while, at the same time, the end which 

 I understand Sir Oliver Lodge desires in the vindication 

 of the reality of mind might be more legitimately achieved 

 if we reminded ourselves at times that the road is a part 

 of the landscape, and that both of them (to recall an old 

 simile), both as they are and as they are known, are the 

 work of the sun. So far from being put forward in the 

 name of any one philosophy, this point of view, I main- 

 tained, is one which psychologists, pluralists and monists, 

 realists and idealists alike, show a growing tendency to 

 adopt. 



The point at which the difference of attitude I advocate 

 is most likely to come home to the physicist is that which 

 Sir Oliver Lodge himself rightly emphasises in the donkey 

 and carrots illustration. The psychologist only asks him 

 to carry this far enough, following the facts as they take 

 him from animal reaction to conscious volition and deter- 

 mination by ideas, on the chance that, when this point has 

 been reached, a new view of the relation of the terms he 

 has been accustomed to oppose to each other as matter and 

 mind may be seen to be possible, and questions such as that 

 raised by Mr. Culverwell in the letter following Sir Oliver's 

 own in your issue of June 18 as to whether one state of 

 motion in the molecules of the brain could in theory be de- 

 duced from the preceding state, of whatever interest to the 

 physicist, to be irrelevant to the more ultimate question 

 of the reality and efficiency of mind. If the conception of 

 a physical world as opposed to a mental can be shown (as 

 psychologists are agreed it can) to be one which has grown 

 up within the conscious subject as a mode of organising 

 and utilising his experience, what reason can there be for 

 representing matter as an independent reality reacting upon 

 another which we call mind? 



In conclusion, may I say that it seems to me one of the 

 misfortunes of present day specialism that physicists and 

 psychologists, like mind and matter themselves, on the 

 common view (though unfortunately without their pre- 

 established harmony), move in different spheres, writing in 

 different journals, and exchanging words, if at all, from a 

 distance? I am grateful to Nature for its hospitality on 

 the present occasion, and to Sir Oliver for his note 

 of welcome. May I express the hope that he will return 

 the visit and continue the discussion in the pages of Mind? 

 I think I may promise him an equally hearty welcome, and 

 if I am right as to present-day tendencies in psychological 

 science, a congenial atmosphere. J. H. Muirhead. 



Birmingham, June 21. 



