128 



NATURE 



[May 12, 1921 



is further indicated by the large proportion of the 

 genera that are also found in Asia — e.g. 47 per 

 cent, of the genera of Leguminosae occur in 

 Ceylon, 42 per cent, of Gramineae, 30 per cent, of 

 Rubiaceae. The only endemic genus, on the other 

 hand, is Neobracea, in Apocynaceae. Taking the 

 families that show genera confined to northern or 

 to tropical America as being the oldest in those 

 regions, one finds them well represented in the 

 Bahamas. Of twenty-nine that have at least 

 twenty genera in each confined to the regions 

 mentioned, all are represented in the Bahamas but 

 Ericaceae, Gesneraceae, and Saxifragaceae. More- 

 over, they are represented by genera in roughly 

 proportional numbers, the largest ten by 189 

 genera, the next ten by 85, the next by 42, and 

 so on. Proportional representation like this is 

 hard to conceive if there was never any land con- 

 nection. 



The Gyroscopic Compass: A Non-Mathematical 

 Treatment. By T. W. Chalmers. (The 

 Engineer Series.) Pp. x-fi67. (London: Con- 

 stable and Co., Ltd., 1920.) 115. net. 

 The writer of this review read and admired many 

 of the chapters composing this book as they 

 appeared in the Engineer during the opening 

 months of last year. The treatment is entirely 

 non-mathematical in the ordinary sense of the 

 term, and the author is to be congratulated on 

 having produced a book which will appeal to all 

 who are interested in gyroscopic action. More- 

 over, it will be of use to engineers and navigating 

 officers who are responsible for the care of work- 

 ing instruments. 



The book begins with an account of elementary 

 gyroscopic phenomena, and this is followed by a 

 clear explanation of the fundamental action of 

 the compass, which, of course, depends on the 

 rotation of the earth, and in no way on the earth's 

 magnetism. The methods of damping out vibra- 

 tions employed in the various types of instrument 

 in use — the latitude error, north steaming error, 

 the ballistic error, the quadrantal error and its 

 elimination — receive excellent treatment in sub- 

 sequent chapters. The explanations of the funda- 

 mental dynamics involved are clear and sound. 



Having explained fully the principles of a gyro- 

 scopic compass, the author describes in detail the 

 Anschiitz, Sperry, and Brown compasses. The 

 last chapter of the book contains an account of 

 the Anschiitz 191 2 compass. This sequence is 

 not correct, for in two respects that instrument is 

 a pioneer one. 



We have no hesitation in recommending this 

 book. J. G. G. 



The Child Welfare Movement. By Dr. Janet E. 



Lane-Claypon. Pp. xi -1-341. (London: G. Bell 



and Sons, Ltd., 1920.) '^s. net. 

 With a birth-rate nearly as low as it has ever 

 been, and an infantile mortality which is capable 

 of reduction by 30 or 40 per mille, the 

 subject of the preservation of child life has 



NO. 2689, VOL. 107] 



assumed great importance. Dr. Lane-Claypon 's 

 book is, therefore, most opportune, and she has 

 compiled a summary of the child-welfare move- 

 ment which for completeness it would be diffi- 

 cult to equal. All aspects seem to have been dealt 

 with, and little has been omitted. This very com- 

 pleteness, however, entails the inclusion of a mass 

 of detail which tends to make the book dull read- 

 ing. 



The author rightly emphasises the import- 

 ance of the breast-feeding of infants, and dis- 

 cusses in an adequate manner artificial substi- 

 tutes. We are inclined to think that she depre- 

 cates unduly the value of milk as a food for older 

 children. While it is true that up to a point other 

 and cheaper foods may take its place, the valuable 

 vitamine content of milk renders it a food second 

 to none, particularly in these days when the 

 cheaper vegetable margarines, which contain no 

 fat-soluble A, have to take the place of butter. 

 Moreover, the milch cow gives a much higher 

 return for the energy-value of her food than does 

 the beef steer. 



We also think that Dr. Lane-Claypon unduly 

 minimises the incidence and effects of venereal 

 diseases on child life, and we have failed to find 

 any reference to the effects of employment and 

 factory life on the expectant mother. 



Appendices occupy nearly 100 pages, and in- 

 clude specimens of leaflets, recording cards, and 

 summaries of various Acts. Orders, circulars, and 

 schemes connected with child welfare. 



Tuberculosis and Public Health. By Dr. H. H. 

 Thomson. Pp. xi4-i04. (London: Longmans, 

 Green, and Co., 1920.) 5s. net. 



This little book gives a concise summary of the 

 problem of tuberculosis in relation to public 

 health. While written primarily for the medical 

 profession, the text for the most part is non- 

 technical, and it should prove of value to non- 

 medical readers who are interested in, or may have 

 to deal with, tuberculosis. The matter is up-to- 

 date; for instance, Brownlee's researches on the 

 different types of pulmonary tuberculosis existing 

 in the British Isles are referred to. 



The author rightly points out the difference in 

 infectivity of the open and closed classes of cases, 

 an appreciation of which simplifies the measures 

 to be taken to prevent the spread of infection. 

 The schemes of treatment and of the care and 

 control of patients outlined are very much to the 

 point, and constitute an adequate summary on 

 these important subjects. In dealing with diag- 

 nosis, a number of useful hints are given on the 

 examination of the chest, the tuberculin reaction, 

 and other aids. 



When discussing the tubercle bacillus the 

 author suggests that it may have a cycle of exist- 

 ence outside the body, and lays stress on the pos- 

 sible spread of tuberculosis among cattle by the 

 fouling of pasture, etc., with the infected excreta 

 of tuberculous beasts. R. T. H. 



