666 SCIENCE PROGRESS 



parts of the book are devoted to a description of the technical production of 

 sugar in all its various stages of purity and also to its refining. The principle of 

 the Diffusion Process is very clearly described in chapter ix, although the 

 last paragraph on page 76 might perhaps be modified somewhat in a future 

 edition. One of the most interesting parts of the book is the one devoted to the 

 by-products of the two industries in which the various suggestions for the 

 utilisation of these materials are set forth. 



The last paragraph sounds a reminder which cannot be too often repeated — 

 " The remarkable technical progress made within the past century has not 

 been effected by the so-called practical man or sugar-producer, but by a 

 comparatively small number of men who built the theoretical foundations 

 upon which modern practice stands." 



P. H. 



Chemistry for Public Health Students. By E. Gabriel Jones, M.Sc, F.I.C. 

 [Pp. X + 244.] (London : Methuen & Co., 1920.) 



One of the main difficulties experienced by the student of Public Health 

 Chemistry is that of disentangling the essential details of any chemical 

 operation from the mass of detail presented to him in most of the ordinary 

 textbooks, with the result that much time is lost. In this little book the 

 author has, however, adopted the excellent plan of breaking up his subject- 

 matter under headings so that all operations are treated on a uniform plan of 

 first briefly describing the object, then giving a complete list of apparatus and 

 chemicals required, and finally giving full and clear instructions as to the 

 exact method of procedure. The somewhat troublesome business of inter- 

 preting the results of an analysis is very well handled throughout the book, 

 but nowhere more ably than in the section on water, where the subject is 

 illustrated by a number of typical analyses. The whole subject is very 

 attractively presented, and, besides giving references to and extracts from a 

 number of original papers and reports such as those of the Royal Commission 

 on Sewage Disposal and the Committee for the Investigation of Atmospheric 

 Pollution, the author has included descriptions of the processes employed in 

 manufacturing margarine and for preserving food materials. The book 

 deserves to be widely read by both students of pubUc health and analysts. 



P. H. 



GEOLOGY 



The Evolution of the Earth and its Inhabitants. By Joseph Barrell. 

 Charles Schuchert, Lorande L. Woodruff, Richard Swann 

 Lull, Ellsworth Huntingdon. [Pp. xi + 208, with 38 figures.] 

 (New Haven : Yale University Press ; London : Oxford University 

 Press, 1919. Price los, 6d. net.) 



A series of able and interesting lectures delivered before the Yale Chapter 

 of the Honorary Scientific Society of the Sigma Xi, edited by Prof. R. S. Lull. 

 The book is up to date, and is eminently suitable for the education of young 

 people (and probably also of many older people) in general science. The 

 essays deal in order with The Origin of the Earth, The Earth's Changing 

 Surface and Climate, The Origin of Life, The Pulse of Life, Climate and 

 CiviUsation. We can find Httle to disagree with in these pages. Perhaps 

 it is somewhat too much of an assumption to suppose that the gorilla has in 

 any way degenerated from a previous type ; and perhaps Dr. Ellsworth 

 Huntingdon presses somewhat unduly his well-known theory that changes 

 of climate have influenced progress very largely — though we are by no means 

 in favour of the view that climate has had very little such effect. The 

 possibility of change of cUmate by afiorestation and deforestation appears 

 to have been well proved both in France and in Mauritius, and there is no 



