August 12, 1920 



NATURE 



739 



touched upon. In connection with the production 

 of milk it would have been useful to include a 

 short account of the practice of milk-recording, 

 for the general reader has but little idea of the 

 system and the benefits it confers. 



The methods employed in separating cream 

 and preparing it for churning are fully dealt with, 

 and the chief machinery, such as the separator, 

 the cream ripener, the regenerative heater, and 

 the pasteuriser are described. 



Cheese-making is dealt with by taking Cheddar 

 cheese as a type, and the principles and practice 

 are fully explained, as are also the essential points 

 in the maturing and marketing of the produce. 



Notes on judging cheese and also butter are 

 i>-iven, and should prove helpful, whilst attention 

 is directed to the advantages which have followed 

 the control cf butter in Denmark and cheese in 

 New Zealand. The reproach still to be heard 

 that a lot of home produce is not of the quality 

 that might reasonably be expected is probably 

 warranted, but a great deal is being done to teach 

 proper methods, and an improvement in, quality 

 may be expected throughout the country in the 

 near future. 



Elgie's JVeathcr Book: For the General Reader. 



By Joseph H. Elgie. Pp. xii + 251. (London: 



The Wireless Press, Ltd., 1920.) Price 55. net. 

 This work is essentially for the uninitiated in 

 weather study. The author presupposes no 

 technical knowledge, and has throughout avoided 

 •mathematics and formulae. A rough survey is 

 taken of elementarv meteorology in a way which 

 must commend itself to all who take an interest 

 in ordinary weather changes. In the opening 

 sentences the author appeals to boy or man ; he 

 might also as well appeal to the other sex, who 

 are now taking a keen interest in all branches of 

 iscience. 



The book is divided into fifteen chapters, which 

 separate the subject into well-recognised divisions. 

 A weather vocabulary is given at the end which 

 the reader will find helpful, and in this, as well as 

 in the general text, the latest official and recog- 

 nised publications have been consulted, which is 

 an immense advantage, as meteorology at present 

 :is making rapid strides in its advance. 



Weather and health are doubtless intimately 

 associated, and in this respect reference is made 

 to the close relationship between rainfall and 

 diphtheria, as shown by Sir Arthur Newsholme, 

 the disease varying inversely with the amount of 

 rain. There are few points in the book with 

 which a meteorologist could find fault, and the 

 author certainly imparts a large amount of useful 

 knowledge. 



Selected Studies in Elementary Physics: A Hand- 

 book for the Wireless Student and Amateur. 

 By E. Blake. Pp. viii+176. (London: The 

 Wireless Press, Ltd., 1920.) Price 55. 

 We have here something of a short cut to know- 

 ledge which occupies a peculiar position in scien- 

 tific literature. Addressed to those already 

 NO. 2650, VOL. 105] 



familiar with the phenomena of wireless telegraphy, 

 it assumes some knowledge of electrical matters 

 on the part of the reader, a little mathematics, 

 but an almost complete ignorance of the physical 

 and chemical properties of matter. We do not 

 say that this attitude is necessarily unsound, as 

 there must be many " amateurs " who have tried 

 to run in pursuit of electrical subjects before they 

 could walk, and it is praiseworthy to endeavour 

 to teach them to walk by a quick method, as they 

 are not likely to possess the time or the tempera- 

 ment to plod through more laborious courses. 

 Granted, then, that there is a justification for pre- 

 senting the elements of physics and chemistry in 

 such a severely compressed form, the author dis- 

 plays skill in dealing with his difficult task, 

 although there are some inconsistencies in the 

 degree of knowledge that he assumes his reader 

 to possess. We like, among other things, the 

 way in which the author encourages the student to 

 think in vectors early in his career, and to keep 

 continually in mind the dimensions of the quanti- 

 ties that he is considering. If the reader is en- 

 abled, by taking advantage of the guidance 

 offered, to form scientific habits of thought which 

 he would not have acquired otherwise, the book 

 will be a success. 



The Coolidge Tube: Its Scientific Applications. 

 Medical and Industrial. By H. Pilon. Author- 

 ised translation. Pp. v + 95. (London: Bail- 

 li^re, Tindall, and Cox, 1920.) Price ys. 6d. 

 net. 

 M. Pilon has not been so careful in selecting a 

 translator for his little book on the Coolidge tube 

 as he was in the original material. The French 

 version was excellent, both from the practical 

 point of view and the judicious selection of data 

 bearing upon recent developments in radiography. 

 Curiously enough, passages which in the original 

 present no difficulty to the reader now lack that 

 clearness which any translator should carefully 

 preserve. W^e select a paragraph which explains 

 the first figure in the text: "This rising part, 

 denoted by <?, is on account of the electrons, by 

 traversing from one electrode to the other under 

 the influence of a large potential difference, 

 acquiring such a speed that on encountering gas 

 molecules, they split up. ..." Again, on p. 17, 

 in describing the radiator type of tube, we read : 

 "The limiting power it is capable of bearing oscil- 

 lates between 500 and 600 watts." 



We notice that the letterpress of many of the 

 cfiagrams remains in the French language. The 

 developments of the Coolidge tube and the uses 

 to which it may l>e put will doubtless necessitate 

 a further edition by ,M. Pilon, and we trust that 

 he will then give the English edition more careful 

 consideration. 



Techno -Chemical Receipt Book. Compiled and 



edited by W. T. Brannt and Dr. W. H. Wahl. 



Pp. xxxiii+516, (London: Hodder and 



Stoughton, Ltd., 1919.) Price 155. net. 



This book contains a very large number of recipes 



covering an amazing field. As might be expected, 



