November 24, 189S] 



NA TURE 



75 



•some, on the other hand, give a good idea of the habit of 

 the plants. 



Taking it akogether, the " Synopsis " is a very useful 

 ■addition to the literature of the order, and it will be found 

 .a convenient handbook for reference. 



H. AND J. Groves. 



0(/R BOOK SHELF. 

 The Unconsdoiis Mind. By A. T. Scholield, M.D., 

 M.R.C.S. Pp. vii + 436. (London : Hodder and 

 Stoughton, 1898.) 

 Dr. Schofield has set himself the task of familiarising 

 the English public with the famous German theory of 

 unconscious mental states. In his anxiety to let more 

 accomplished psychologists speak for themselves he has, 

 in many parts of his book, been content simply to re- 

 produce the ipsissima verba of his authorities without 

 criticism. Unfortunately he is himself scarcely psycho- 

 logist enough to distinguish good authorities from bad, 

 and trusts far too implicitly to the crudities and vagaries 

 of such writers as Eduard von Hartmann. His work will 

 hardly do much towards shaking the conviction of most 

 English students of the science that "unconscious 

 mind" is much such another phrase as "invisible colour" 

 or " unextended body." Unconsciousness seems to mean 

 very different things for him in the course of his argument. 

 Instinct, he says, belongs to the "unconscious mind," 

 because the animal executing the instinctive movement is 

 unaware of its purpose. This seems quite unreasonable ; 

 the instinctive act is conscious enough in the sense of 

 being attended both with sensation and with pleasure or 

 pain ; how then does the absence of knowledge of its 

 biological value make it " unconscious " ? Again we hear 

 of " unconscious sensations," but they seem to mean no 

 more than neural changes which would, under other con- 

 ditions, be attended with consciousness. But surely it is 

 obvious that it is one thing to say that if my attention had 

 not been preoccupied a certain neural change would have 

 resulted in a conscious sensation, and quite another to say 

 that it has actually produced a sensation in my " un- 

 conscious mind." The unconscious execution of habitual 

 mechanical processes is, of course, said to be presided over 

 by " unconscious, mind " ; but where does the need of this 

 undefined tertium quid come in ? What is there, apart 

 from the unscientific assumption as to the absolute hetero- 

 geneity of the psychical and physical, to prevent our 

 saying quite simply that as a process becomes habitual 

 and unconscious it ceases to be mental at all and becomes 

 purely nervous ? The believers in " unconscious mind " 

 indeed profess to find it unthinkable that a combination 

 of psychical elements should come to be replaced by a 

 combination of physical elements, but they seem to have 

 no better reason for their view than what Ebbinghaus 

 well calls "this vulgar prejudice of the absolute distinc- 

 tion between mind and matter." It is probably not too 

 much to say that Leibnitz's invention of the "petites 

 perceptions " and Herbert's unlucky metaphor of the 

 "threshold of consciousness " are responsible between 

 them for an incalculable amount of psychological myth- 

 making and confusion. Far the most valuable part of 

 Dr. Schofield's book, the chapters in which he relates 

 facts as to the therapeutic \'alue of mental influences, is 

 quite independent of his psychological theory. 



A. E. Taylor. 



Higher Arithmetic. By W. W. Beman and D. E. Smith. 



Pp. .xvi -I- 193. (London : Ginn and Co., 1897.) 

 The book before us is for the service of teachers. It 

 is not intended as a first course, but for those who have 

 already had some experience, and wish to review and ex- 

 tend their knowledge. 



NO. 15 17, VOL. 59] 



The authors have adopted quite a new line of treat- 

 ment, and instead of making the subject into a set of 

 puzzles, as is so often done, they have introduced many 

 improvements by showing how the subject is applied to 

 every-day use. Thus we have a chapter on " Longitude 

 and Time," and the reader is made acquainted with the 

 relationship between them, together with the excellent 

 system of universal time in use in the United States and 

 nearly all over the world. Again, it is pointed out how 

 a knowledge of arithmetic is applied to solve problems in 

 elementary electricity. From the beginning to the end 

 of the book the authors have made it their chief aim to 

 point out the utility of the subject in its various applica- 

 tions. The book contains, besides an excellent list 

 of definitions and etymologies arranged alphabetic- 

 ally, a great number of well chosen and appropriate 

 examples. 



The Story of Marco Polo. With Illustrations. Pp. xiv 



-I- 248. (London : John Murray, 1898.) 

 The preface is signed " Noah Brooks," and the little 

 book is prepared specially for young readers. The plan 

 is excellent, and well carried out. Selected extracts Irom 

 Yule's " Book of Ser Marco Polo" are accompanied and 

 woven together by a pleasantly written commentary, 

 which seems to have been designed to interest the young 

 people of the United States and the United Kingdom. 

 Nothing could be better for the purpose. The extra- 

 ordinary fidelity of many of Marco Polo's descriptions to 

 fact is pointed out, and the incredulity with which they 

 were received in a credulous age is duly dwelt on : a 

 few of the more fanciful passages are also given, and the 

 antiquity of these old stories noted. Probably many 

 older people will see with surprise the minute exactness 

 with which Marco Polo, six hundred years ago, described 

 some of the most marvellous stock tricks of the modern 

 Indian conjurers. The illustrations are not numerous, 

 but very graceful and well selected. A map would have 

 been a desirable addition. H. R. M. 



L'Art de Dccoitvrir les sources et de les Capter. By 

 E. S. Auscher. Pp. 278. (Paris ; J. B. Bailli^re et 

 Fils, 1899.) 

 Beginning with the physical properties of water, and 

 dealing in order with the substances usually found dis- 

 solved in natural waters, the sources of these soluble 

 materials, and the geological nature of the rocks through 

 which subterranean waters percolate, the reader is intro- 

 duced to the methods of water analysis in common use. 

 The arrangement of strata and the characteristics of 

 common rocks arr explained with a view to making the 

 circulation of underground waters easily understood. 

 The third division of the volume, dealing with " La 

 recherche des sources et des eaux souterraines," includes 

 a chapter on " les signes e.xterieurs," which is only of 

 doubtful scientific value, though many water-diviners 

 doubtless receive great guidance from such consider- 

 ations. Several of the illustrations are ingenious, and 

 the book will be interesting to civil engineers who are 

 concerned with questions of water supply. 



Handbook of Insects Injurious to Orchard and Bush 

 Fruits., with Means of Prevention and Remedy. By 

 Eleanor A. Ormerod. Pp. x -f 286 ; portrait and wood- 

 cuts. (London : Simpkin, Marshall, Hamilton, Kent, 

 and Co., Ltd., 1898.) 

 Miss Ormerod has now added to her long and useful 

 series of works on agricultural entomology by pub- 

 lishing a volume specially devoted to the insects and 

 mites injurious to fruit. It is hardly necessary to say 

 that the book is worked out in her usual careful manner, 

 and freely illustrated. The principal fruits are arranged 

 in alphabetical order, commencing with apple ; and 



