September io, 1914] 



NATURE 



n 



subject, and exhibit its practical bearing-. It is 

 the best collection of mathematical examples we 

 have yet met. 



(9) Now that an experimental course of statics 

 has obtained a firm foothold in the school curricu- 

 lum, it is possible to introduce boys of no special 

 mathematical talent to certain features of theo- 

 retical work. In addition to the elements of 

 geometry and algebra, nothing more than a know- 

 ledge of the trigonometry of the right-angled 

 triangle is needed for applications of all the 

 fundamental ideas which make this subject educa- 

 tionally valuable. 



The volume before us contains just what is 

 needed for work of this character. It opens with 

 the use of pulleys and the ideas of work, power, 

 velocity-ratio, and efficiency. Then follow simple 

 cases of moments and applications to the more 

 important machines. In this way the student is 

 led at once to see the practical utility of the work, 

 and is able by experiment to clarify his conception 

 of force, etc. No use is made of the parallelogram 

 and triangle of forces until comparatively late in 

 the course, and formal bookwork proofs are post- 

 poned to the end. The examples are chosen so 

 as to illustrate the principles of mechanics rather 

 than to test the student's analytical ability. 



(10) We are glad of this opportunity of direct- 

 ing attention to the work that is being done by 

 the London Mathematical Society. All those who 

 are interested in any branch of higher mathe- 

 matics, whether they hope or intend to do any 

 research work or not, should apply for election. 

 Only in this way is it possible for students to 

 keep in touch with the trend of modern develop- 

 ments when their University days are over. 



OVR BOOKSHELF. 

 British Rainfall, 19 13. Compiled under the direc- 

 tion of H. R. Mill. By R. C. Mossman and 

 C. Salter. Fifty-third annual volume. Pp. 

 92 + 384. (London: E. Stanford, Ltd., 1914.) 

 Price 10s. 

 This valuable publication is well known to readers 

 of Nature, having been frequently referred to in 

 its columns. The fundamental part of the work 

 includes : (i) general tables of total rainfall, and 

 (2) observers' remarks on the weather; these are 

 of great interest, and refer mostly to exceptional 

 phenomena. The discussion of the data deals 

 inter alia with monthly and seasonal rainfall, 

 heavy daily falls, and the relation of the annual 

 rainfall to the average. A great rainstorm of 

 September 17, which was most intense near Don- 

 caster, is illustrated by a coloured plate ; the area 

 with more than an inch of rain in about fourteen 

 hours comprised more than 1300 square miles. I 

 The rainfall of the year over the whole of the I 

 British Isles was almost exactly equal to the 1 



NO. 2341, VOL. 94] 



average of thirty-five years (187 5-1909). Ihe ex- 

 cess in Wales was 9 per cent, and in Ireland 7 

 per cent. ; elsewhere there was, generally speak- 

 ing, a deficiency. The volume includes three 

 special articles : (i) an appreciative memoir of the 

 late Sir John Murray, who represented Scotland 

 on the Board of Trustees of the British Rainfall 

 Organisation; (2) the dry summer of 1913 — in 

 July and August the rainfall deficiency was 60 per 

 cent, over the United Kingdom as a whole; (3) 

 frequency of heavy rains in short periods, 1868- 

 1913. The useful work of the organisation is 

 dependent upon voluntary contributions, but un- 

 fortunately it is not self-supporting; the director 

 has to meet considerable deficiencies, consequently 

 application for Government aid has become 

 necessary. 



Handbook of Photomicrography. By H. Lloyd 

 Hind and \V. Brough Randies. Pp. xii-f 292 + 

 44 plates. (London : George Routledge and 

 Sons, Ltd., n.d.) Price 75. 6d. net. 

 This book gives a useful and adequate account 

 of the theory and practice of photomicrography. 

 It is written from the point of view of the be- 

 ginner and amateur, and full explanations are 

 given of the principles governing the results aimed 

 at and of the methods for obtaining these results. 

 Photomicrography with the lowest and highest 

 powers is dealt with, and wherever possible simple 

 and home-made apparatus is described. In addi- 

 tion to photomicrography proper, the various 

 photographic processes are explained and de- 

 scribed, and methods of making lantern slides, 

 colour photography, and the preparation and 

 mounting of objects are included. The book is 

 well produced and profusely illustrated both by 

 figures in the text and with forty-four plates, 

 several of which are coloured and reproduced 

 from direct colour photographs. The plates 

 illustrate very well the different results that can 

 be obtained with different methods of. illumina- 

 tion, various objectives and varying adjustments. 

 We believe that Messrs. Hind and Randle's hand- 

 book will be found a very useful work on the 

 subject of photomicrography. 



The Microscopy of Drinking Water. By Prof. 



G. C. Whipple. Third edition, rewritten and 



enlarged. Pp xxi + 4C)9 + xix coloured plates. 



(New York : J. W^iley and Sons, Inc. ; London : 



Chapman and Hall, Ltd., 1914.) Price 175. net. 



We are glad to welcome the third edition of this 



valuable book. Since the first edition was issued 



in 1880 an enormous amount of work has been 



devoted to the study of the microscopic organisms 



in water, and the increase in size of the present 



edition bears witness to this. The mystery of the 



comings and goings of various groups of algje 



and protozoa in our lakes and reservoirs still, 



however, remains unsolved. From the practical 



side much progress has been made in the artificial 



means of controlling Plankton growths and the 



purification of waters containing them. 



The first part of the book has been almost re- 

 written, and contains chapters on copper treat- 

 ment for eradication of algae, the soil-stripping of 



