July 21, 1921] 



NATURE 



647 



system should be corrected in another edition, as 

 should also a few misprints (especially on p. 319). 

 These are, however, matters of minor importance. 

 Taken as a whole, the book appears to be care- 

 fully and attractively written, and is illustrated 

 by photographs of both minerals and crystal 

 models, though it is doubtful whether the latter 

 are really more effective than the line drawings 

 that accompany them. There are also photo- 

 graphs of distinguished mineralogists, past and 

 present, but a caveat must be entered to the 

 ■claim that Werner was the first to place 

 mineralogy on a scientific basis. The credit of 

 the foundation of the science must be shared bv 

 some of his predecessors, such as Cronstedt, as 

 well as by contemporaries like Kirwan. 



John W. Evans. 



Our Bookshelf. 



Elements of the Mathematical Theory of Elec- 

 tricity cmd Magnetism. By Sir J. J. Thomson. 

 Fifth edition. Pp. viii + 410. (Cambridge: 

 At the University Press, 192 1.) 305. net. 



Earlier editions of this book were fully reviewed 

 in Nature, but the alterations and improvements 

 in the present edition deserve special notice. One 

 ■change — that in the treatment of hysteresis — 

 makes the subject of energy dissipated in the mag- 

 netic field much clearer to the student. A piece 

 of iron is put through a magnetic cycle and it is 

 imagined as being displaced from one position in 

 the field to another. The thing emphasised is the 

 work done in effecting a displacement of a mag- 

 netic element in the field, which is ZaISH, where H 

 is the field intensity, I the intensity of magnetisa- 

 tion, and la the volume of the element. The 

 former way of putting the matter puzzled the 

 thoughtful student, while the thoughtless person 

 accepted it without analysis of its meaning. It 

 was said that "the diminution in the potential 

 energy when the magnet moves into the stronger 

 field is laiSH." The change in potential energy 

 was not this, but Za(ISH + H5I), and the thinker 

 Tiaturally wondered what had become of the term 

 iaH5I. 



The most natural and convincing method of 

 •considering this matter is that due to the late 

 Dr. John Hopkinson, and given when an attempt 

 was made (not in this book) to demonstrate the 

 hysteresis formula by juggling with the terms of 

 the variation of a perfect differential. This 

 method of Hopkinson's is to be found on p. 339. 

 It considers the work thrown into the field from 

 the battery when the magnetisation is changed by 

 a magnetising current. 



An interesting discussion of a gas the molecules 

 of which are small magnets has also been added. 



On the whole this edition of a sound and popular 

 book is brought well up to date. All the altera- 

 tions will be thoroughly appreciated by the 



NO. 2699, VOL. 107] 



student except that in the price, which has made a 

 prodigious leap. It is a difficult time, as every- 

 one knows, but many a student who would have 

 willingly added this book to his own little stock 

 of standard works will have to content himself 

 with borrowing it. A. Gray. 



Metabolism and Growth from Birth to Puberty. 

 By F. G. Benedict and F. B. Talbot. (Publica- 

 tion No. 302.) Pp. vi + 213. (Washington: 

 The Carnegie Institution of Washington, 1921.) 

 Benedict and Talbot's work on the "Metabolism 

 and Growth from Birth to Puberty " of children 

 of both sexes aged from one week up to fifteen 

 years is a continuation of that on new-born infants 

 published six years ago. The children were all 

 physiologically normal, and some of the data are 

 from the same children at different ages. 

 Measurements of the weight, height, pulse-rate, 

 and body-temperature are recorded, as well as the 

 basal metabolism figures — i.e. the heat evolved in 

 twenty-four hours in the subject at quiet repose 

 and in the post-absorptive condition. These con- 

 ditions were not easy to attain in the case of in- 

 fants; there was not usually quiet repose unless 

 some food was in the alimentary tract, but occa- 

 sionally measurements were made as long as nine 

 hours after a meal. The data are thus rather 

 above the real basal figures than below. The 

 basal metabolism is referred to age, weight, 

 height, and body surface in a series of curves. 

 The body surface was calculated by the Du Bois 

 formula from actual measurements. Weight and 

 height run parallel with age, and the basal meta- 

 bolism increased from approximately 150 to 

 1100 Calories. In comparison with body surface 

 the basal metabolism rose rapidly during the first 

 year; after this age there was a continual de- 

 crease. There was no marked difference between 

 the sexes, but after reaching the weight of 1 1 kilo- 

 grams boys had a slightly higher metabolism than 

 girls. All the data for basal metabolism are lower 

 than those recorded by previous investigators. 

 The publication is a valuable contribution to 

 physiological literature. 



•Chemistry. By G. H. J. Adlam. (" Science for 

 All" Series.) Pp. x-f238. (London: John 

 Murray, 1921.) 35. 6d. net. 

 The book under notice is intended for a beginner 

 who is " guided and inspired by a competent 

 teacher." Many recent discoveries are included 

 and the material is, on the whole, presented in an 

 accurate and readable form. Several minor errors 

 are, however, noticeable. Glaziers' "diamonds" 

 are not " splinters " (p. no); oxygen is not used 

 in determining the flash-point of an oil (p. 119); 

 the experiment described on p. 157 seems unlikely 

 to succeed ; the recovery of sulphur from alkali- 

 waste is not without value (p. 170); and the 

 carbon arc is not used in the fixation of nitrogen 

 (p. 184). -The atomic theory is explained only at 

 the end of the book, although the method of count- 

 ing the a-particles expelled from radium is referred 

 to on p. 10. 



