53« 



NATURE 



[February 23, 191 1 



The first nine chapters deal with machines and such 

 details connected with them as frictional losses, energy 

 of moving masses, relative velocities and accelerations, 

 and output of work. There is an excellent chapter 

 on simple harmonic motion, in which many of the 

 difficulties are smoothed away which generally worry 

 the young student entering for the first time on the 

 study of this branch of the subject. The latter half 

 of the book is devoted to stress and strain, bending 

 moments, shearing forces, and stresses in beams, the 

 stresses and amount of twist in shafts when trans- 

 mitting power, and the stresses in simple loaded 

 frameworks ; it is rather stranpfe that the authors 

 have entirely omitted to deal with the deflection of 

 beams. The last chapter is devoted to a simple treat- 

 ment of the problem of the flight of projectiles. 



The two authors have succeeded in writing on a 

 well-worn subject a text-book which will be welcomed 

 by many young engineering students because of the 

 clear and lucid way in which fundamental principles 

 are explained and enforced. 



(2) This book is based upon the lectures delivered 

 by the author to the students at the Technical College, 

 Finsbury, London, and it covers more ground than is 

 usual in the case of the more advanced text-books on 

 this subject. 



The first thirteen chapters are devoted to a con- 

 sideration of the laws of motion, work, and energy; 

 friction ; the energy of rotating masses ; centres of 

 gravity, &'c. There is nothing novel in the treatment 

 of the subject, but fundamental principles are clearly 

 enunciated and explained, and fully worked out 

 examples are freely used in order to illustrate the 

 application of these principles to the many practical 

 problems which the engineer is called upon to solve. 



The next eight chapters deal with the branch of the 

 subject usually termed " Strength of Materials." Two 

 excellent chapters on simple harmonic motion, and the 

 balancing of rotating masses, are included in these 

 eigfht chapters ; in any future edition it would be an 

 advantage to print these chapters immediately after 

 chapter x. of the present edition, as this is the correct 

 sequence for them. 



The remainder of the book is devoted to elementary 

 h^-draulics and to the elements of the theory of the 

 steam engine, including in the latter case such 

 problems as the effects produced by the inertia of the 

 reciprocating masses, the dynamics of steam engine 

 g-overnors, valve gears, and their effect upon the steam 

 distribution. A four-figure table of logarithms is 

 printed as an appendix, and will prove useful to 

 students who are working through the problems given 

 at the end of the book. The book will probably prove 

 useful to junior students in technical colleges. 



OUR BOOK SHELF. 



The Microscopical Examination of Food and Drugs. 



By Prof. H. G. Greenish. Second edition. Pp. 



XX4-386. (London : J. and A. Churchill, 1910.) 



Price J2S. 6d. net. 

 The general excellence of this standard work, which 

 first appeared in 1903, is maintained throughout the 

 second edition, and its usefulness is increased by the 

 addition of a valuable section or^ adulterants and an- 



NO. 2156, VOL. 85] 



other on the practical examination of unknown 

 powders. Other new subjects which have been intro- 

 duced include notes on saffron and gentian, liquorice 

 and calumba roots, and a description of a method of 

 preparing fibres for cutting transverse sections. 

 Otherwise no change has been made in the method 

 of treating the subject-matter ; and, indeed, none was 

 necessary. 



The first section deals with the various starches, 

 complete instructions being given as to how to mount 

 specimens for microscopic examination ; the author 

 describes the shape and appearance of the starch and 

 explains how the grains can be sketched to their 

 correct relative size. In subsequent chapters hairs and 

 textile fibres, spores and glands, roots, woods, stems, 

 leaves, flowers, barks, seeds, fruits, rhizomes, and 

 roots are dealt with in an equally complete manner, 

 and care has been taken to select types which will 

 best illustrate the methods of examination described. 

 With regard to foods, the book is essentially a treatise 

 on practical methods rather than a complete guide to 

 their examination. 



In a future edition the inclusion of more foods 

 would make the book of still greater use to analysts, 

 but those at present included are well and adequately 

 dealt with. In the very useful section on adulterants, 

 oil cake might also have been treated from the point 

 of view of the adulteration of oil cake itself; and, in 

 passing, it may be noted, as a very minor point, that 

 in giving the sources of oil cake, the author omits to 

 mention cotton seed. The original illustrations are 

 carefully drawn as to detail, and the drawings selected 

 from other authorities are well chosen. The book 

 will continue to be of great value to students and 

 analytical chemists, as well as to those pharmacists 

 who pursue their calling in its higher branches. 



Child Problems. By Dr. G. B. Mangold. Pp. xv + 

 381. (New York: The Macmillan Co.; London: 

 Macmillan and Co., Ltd., 1910.) Price 5s. net. 

 In this volume the author deals principally with facts 

 and figures obtained from American sources, but the 

 problems are similar to those which were brought 

 into prominence in England in 1904, when evidence 

 was given before the Interdepartmental Committee on 

 the causes of physical deterioration. Prevention is 

 better than cure, and the hope for the future must 

 always be with the younger generation. In some 

 respects America is ahead of England. The deplor- 

 able waste of child-life owing to preventible causes is 

 recognised as a national concern, and in many of the 

 States there is a more or less efficient supervision 

 and regulation of the milk supply. Separate courts 

 for children have been established for some years in 

 several of the States, and the whole attitude of 

 society towards the youthful delinquent appears to 

 offer more chance of reforming him than does the 

 English system. In other respects possibly America 

 might learn from England, e.g. in regard to factory 

 legislation. 



Social problems appear under somewhat different 

 aspects in different countries, but all civilised com- 

 munities are beginning to realise that national 

 efficiency depends on prevention of the causes which 

 lead to physical deterioration, and a study of the social 

 problems connected with childhood has world-wide 

 application. 



"The child is father to the man": the physical, 

 moral, and intellectual welfare of the race depend on 

 the inheritance, training and education of the chil- 

 dren. Child problems are the gravest of our tiire and 

 the present volume should prove helpful to all who 

 are anxious to further reform. The subject matter is 

 dealt with under five heads : infant mortality, educa- 



