August 19, 1920] 



NATURE 



in 



ment, the imitation of seal impressions, the 

 forgery of postage stamps, and the examination 

 of handwriting are also briefly touched upon in 

 this section, whilst there is a cognate section upon 

 the detection of robbery from letters and parcels 

 in transit. 



Other subjects which are discussed include the 

 examination of dust and stains, the development 

 of finger-prints, the investigation of the cause of 

 fires and of damage to crops, and the examination 

 of fibres, ropes, and clothing. In each case refer- 

 ences to literature on the subject are appended, 

 and illustrative cases usually given. 



Regarded as a whole, the book should be wel- 

 comed by every chemist whose work is likely to 

 include any problems in which legal questions are 

 involved, and it might well be made the nucleus of 

 a more comprehensive work on forensic chem- 

 istry. It is sometimes urged against the publica- 

 tion of details of scientific methods as applied to 

 the detection of crime, such as are given here, 

 that it is dangerous to provide prospective 

 criminals with information in a convenient form 

 for reference ; but this objection applies with more 

 cogency to the publication of the scientific methods 

 of combating the adulteration of food. The 

 adulterator is frequently waiting to be made ac- 

 quainted with the scientific drawbacks of his 

 methods, whereas the persons who commit other 

 forms of fraud are nearly always without scientific 

 training and, if they were to attempt to avoid one 

 scientific pitfall, would be almost certain to fall 

 into another. C. A. M. 



Our Bookshelf. 



Optical Projection. By Lewis Wright. Fifth 

 edition, rewritten and brought up to date by 

 Russell S. Wright. (In two parts.) Part i., 

 The Projection of Lantern Slides. Pp. viii + 87. 

 (London : Longmans, Green, and Co., 1920.) 

 Price 45. 6d. net. 

 This completely revised edition of Mr. Lewis 

 Wright's bo6k is very welcome. We are glad to 

 see that the oil-lantern, which is so handy in small 

 class-rooms and in the huts of camps, is still re- 

 garded as a possible projector. It may be men- 

 tioned that if this lantern is filled for each occa- 

 sion, and set up lighted in an adjacent room, or, 

 better still, in the school-yard, for forty minutes 

 or so before the lecture, all risk of producing 

 offensive fumes will be avoided. In regard to 

 screens for such class-rooms, may we add that a 

 square of mounted diagram-paper, which is made 

 5 ft. wide, gives an excellent surface, and can 

 be kept rolled up and fixed with large drawing- 

 pins as required? Lastly, when Mr. R. S. Wright 

 gives suggestions as to flash-signals, should he 

 even tolerate the "next slide " system of com- 

 NO. 2651, VOL. 105] 



munication with the operator? The recently intro- 

 duced silent wave of the pointer has escaped 

 mention in this useful treatise. G. A. J. C. 



Elementary Agricultural Chemistry : A Handbook 

 for Junior Agricultural Students and Farmers. 

 By Herbert Ingle. Third edition, revised. 

 (Griflin's Technological Handbooks.) Pp. ix 

 4-250. (London : Charles Griffin and Co., Ltd., 

 1920.) Price 55. 

 There are no essential differences between this 

 and the second edition of Mr. Ingle's book. The 

 volume provides an excellent introduction to its 

 subject in a form which should be intelligible to 

 the practical agriculturist as well as to the scien- 

 tific student. It contains a number of interesting 

 and useful tables, and on account of its very 

 reasonable price it should be popular with students 

 of agriculture. Although described on the cover 

 as "A Practical Handbook," it contains no 

 account of experiments or methods of analysis, 

 but these would no doubt have increased the size 

 of the book beyond the limits desired. 



Luck, or Cunning, as the Main Means of Organic 

 Modification? An Attempt to Throw Addi- 

 tional Light upon Darwin's Theory of Natural 

 Selection. By Samuel Butler. Second edition, 

 re-set, with author's corrections and additions 

 to index. Pp. 282. (London : A. C. Fifield, 

 1920.) Price 85. 6d. net. 

 This is a reprint of the first edition pub- 

 lished in 1886. The only important changes 

 are in the index, which has been considerably 

 enlarged by additions made irom notes by the 

 author In a copy of the first edition. As is an- 

 nounced in the introduction, the book is written 

 round Samuel Butler's favourite theories, "the 

 substantial identity between heredity and 

 memory," and "the re-introduction of design into 

 organic development." 



Notes on Chemical Research: An Account of 

 Certain Conditions which apply to Original 

 Investigation. By W. P. Dreaper. Second 

 edition. (Text-books of Chemical Research and 

 Engineering.) Pp. IV-M95. (London: J. and 

 A. Churchill, 1920.) Price 75. 6d. net. 

 The first edition of this stimulating work was 

 reviewed in Nature for February 6, 191 3. The 

 new edition is divided into two portions, the first 

 dealing with the history and method of research, 

 and the second with modern works practice. A 

 chapter in the latter portion is given up to the 

 consideration of the training desirable for a re- 

 search student. An index would have been 

 helpful. 



Spiritual Pluralism and Recent Philosophy. By 

 C.A.Richardson. Pp. xxi + 335. (Cambridge: 

 At the University Press, 1919.) Price 145. net. 

 The author examines the Weber-Fechner law of 

 sensation and shows that "unperceived sense- 

 data," such as are sometimes deduced from it, are 

 not logically admissible. He expresses spiritual 



