March 4, 1920] 



NATURE 



valuable space with an account of soils and soil 

 analysis which the reader could far better obtain 

 elsewhere. Yet there is scarcely a more vital in- 

 dustry at the present time than the manufacture 

 of, artificial fertilisers, nor is its importance likely 

 to diminish. 



The best chapters are the two on pebble phos- 

 phate and on hard-rock phosphate. The Florida 

 phosphates are usually classified into four groups : 

 hard rock, soft rock, land pebble, and river pebble, 

 all of which occur in the Eocene and more recent 

 formations. Of these the hard rock is the purest, 

 containing phosphate equivalent to 80-85 P^^ cent, 

 of dicalcic phosphate ; the land pebble contains 

 somewhat less, while for the soft rock and river 

 pebble the corresponding figures are about 55 to 

 68 per cent. The method of working is fairly 

 well described. The remaining chapters, however, 

 are not so good. More information might have 

 been given about the mechanical dens and other 

 contrivances used in the manufacture of super- 

 phosphate. Scarcely anything is said about the 

 manufacture of mixed manures, although this is 

 one of the largest branches of the business. The 

 chapter on the fixation of atmospheric nitrogen is 

 some years out of date ; no mention is made of the 

 Haber or the Ostwald process ; the old view, now 

 given up elsewhere, is still put forward, that 

 cyanamide changes to "dicyanamide " (dicyano- 

 diamide) and then to ammonia by bacterial action. 



Should a second edition be called for, the author 

 would be well advised to omit the chapters on soil 

 and the science of manuring. It might also be 

 wise to ask a chemist to read the proofs in view 

 of his gibe about treatises on agricultural analysis 

 with methods which the student "would have to 

 unlearn if he entered a fertiliser factory, where he 

 would have to analyse manures against chemists 

 of some reputation." The reader would thus be 

 spared some interesting specimens of chemistry 

 which we hope are not typical of the new chem- 

 istry given in American fertiliser factories in place 

 of the unlearned college work, such as : — 



"The sodium chloride decomposed by the free 

 phosphoric acid caused the bags to burst in transit, 

 for there is no substance which rots bags like free 

 chlorine and fluorine — two elements give/i off when 

 nitrate and damp superphosphate are mixed." 



E. J. Russell. 



Our Bookshelf. 



Telephony without Wires. By Philip R. Coursey. 



Pp. xix + 414. (London: The Wireless Press, 



Ltd., 1919.) Price 15^. net. 

 This book gives a fairly complete account of the 

 practical development of radio-telephony. Accu- 

 rate descriptions are given of very many types of 

 NO. 2627, VOL. 105] 



apparatus. The book, therefore, is more useful 

 for reference than for learning the principles of 

 the art. Little space is devoted to theoretical con- 

 siderations, but the author mentions some of the 

 difliculties encountered, and indicates possible lines 

 of advance. The bibliography is very complete, 

 some 700 references being given to original papers 

 on the subject. 



From the commercial point of view, radio- 

 telephony is not very attractive at present, as its 

 applications are mainly confined to those cases 

 where the ordinary telephone service' cannot be 

 used. It is possible by using very costly apparatus 

 to telephone on land over thousands of miles. For 

 instance. New York and San Francisco were put 

 in telephonic communication in November, 1917, 

 although the distance is 3400 miles. The experi- 

 ment was successful, but it did not prove the 

 commercial feasibility of such a long-distance 

 service, as the value of the apparatus. in ^se' when 

 talking was 400,000/. . .1 ; 



Radio-telephony was very useful iti the later 

 months of the war, as communication was estab- 

 lished by its use not only between aeroplanes and 

 the earth, but also directly between aeroplaiies. ' It 

 has also proved useful in establishing fcbmmunica- 

 tion between moving trains and the ordinat'v fixed 

 telephone systems. During the last few ; years 

 the rapid development of radio-telephony has been 

 mainly due to the researches of the physicist and 

 the mathematician. The problems it fvirnishes 

 are of absorbing interest, and it is rapidly widen- 

 ing our knowledge of the laws of Nature. 



Scientific Method: Its Philosophy and.its Practice. 



By F, W. Westaway. New edition. Pp. ,\%i+ 



426. (London: Blackie and Son, Ltd., 1919.) 



Price 10s. 6d. net. 

 Sir J. J. Thomson's committee on the position 

 of natural science in the educational system of 

 Great Britain expressed agreement with the view 

 that "some knowledge of the history and philo- 

 sophy of science should form part of the intel- 

 lectual equipment of every science teacher in a 

 secondary school." There is no more enlightening 

 and helpful volume from which to acquire such 

 knowledge than this by Mr. Westaway. The 

 implications of scientific reasoning, method, and 

 practice are clearlv presented, and the examples 

 are both apt and instructive. Any science 

 teacher, whether in university or school, who 

 reads the book cannot fail to derive profit and 

 interest from it. - . 



In this second edition the chapter on " Philo- 

 sophers and Some of their Problems " has been 

 re-written, and is now a more precise statement 

 of the specific claims of philosophy than was the 

 chapter in the original issue. A new appendix, 

 entitled "Retrospect and Reflections," sugveys the 

 function and influence of science and scientific 

 method in national life, superseding one on " .^n 

 American School Course in Chemistry." The index 

 is missing in our copy of the book, though there 

 was one in the first edition, but its absence is 

 possibly due to a fault of the binders. 



