April 22, 1920] 



NATURE 



229 



on " The True Mahoganies," by Mr. R. A. Rolfe, 

 and "The Jerusalem Artichoke," by Mr, C. C. 

 Lacaita ; the latter is an exhaustive discussion on 

 the introduction of this vegetable to the Old 

 World and the origin of its popular name. An 

 account is given of Lord \'entry's experiments 

 on growing New Zealand flax in Ireland; the evi- 

 dence goes far to show that the possibility of 

 growing it in South-West Ireland as a commercial 

 undertaking is an established fact. " Silver-leaf 

 Disease" and "The Skin-spot Disease of Potato- 

 tubers " are the titles of two important con- 

 tributions on plant-diseases by Messrs J. Bintner 

 and M. Nest Owen respectively. Results of 

 botanical exploration are embodied in Dr. Hems- 

 ley's account of the flora of Aldabra and adjacent 

 islands and in Mr. Turrill's resume of the botani- 

 cal results of Swedish South American and Ant- 

 arctic expeditions. 



The more purely botanical papers include a 

 careful examination, by Sir David Prain and Mr. 

 Burkill, of the identity of the plant, or plants, 

 known under the name Dioscorea sativa; and a 

 revision by Mr. W. B. Grove of the species of the 

 fungus genus Phoma. There is also an historical 

 account of the botanic garden of Pamplemousses, 

 Mauritius ; and the new flagstaff at Kew and its 

 erection are described in detail. The obituary 

 notices include those of Prof. J. W. H. Trail 

 of Aberdeen and Prof. W. G. Farlow of Harvard. 



The Story of Milk. By J. D. Frederiksen. 

 Pp. XX +188. (New York: The Macmillan 

 Co.; London: Macmillan and Co., Ltd., 1919.) 

 Price 95. net. 



The author tells his story in a clear and interest- 

 ing manner, and the general reader, as well as 

 the student of domestic science or dairying, will 

 follow the contents of the book with pleasure and 

 profit. The subject-matter is sound, and the 

 concise, practical directions will be valuable to 

 anybody who is acquainted with the general 

 methods of butter-making and cheese-making. 



There are sections dealing with the composition 

 and properties of milk, the testing of milk, the part 

 played by enzymes and bacteria, and the methods 

 by which organisms are utilised or controlled. 

 Milk supply and butter-making and the manu- 

 facture of ice cream are the chief subjects of 

 another section. As the book is written for 

 American readers, the sixteen pages devoted to 

 recipes for ice cream are perhaps not excessive, 

 and they will not fail to raise in the English mind 

 a feeling of envy that such delectable things as 

 parfaits and mousses are not more general. 



Cheese-making is well dealt with, and working 

 details are supplied, whilst the methods adopted in 

 the manufacture of condensed milk, milk powder, 

 and casein are briefly sketched. 



Very rightly the food value of milk is given a 



prominent place, and the recipes for dishes in 



which milk or cheese forms an important part are 



attractive, and should be found very useful to 



NO. 2634, VOL. I05I 



many. A certain, amount .of historical informa- 

 tion is given, and the names and labours of notable 

 workers in the various branches of dairying are 

 also to be found in the book. 



A First Year Physics for Junior Technical Schools. 

 By G. W. Farmer. With an Introduction by 

 S. C. Laws. Pp. X 4- 183. (London : Long- 

 mans, Green, and Co., 1920.) Price 45. 6d. 

 This book is intended for use by boys of be- 

 tween twelve and fourteen years of age who have 

 just completed the elementary-school course and 

 are passing to a more advanced curriculum such 

 as is provided in the junior technical, central, or 

 continuation school. It may suit the courses in 

 some of these institutions, but if this is to be the 

 only kind of instruction in physics during the first 

 year of study, the diet cannot be said to be too 

 stimulating. The work is concerned almost entirely 

 with the use of simple measuring instruments. 

 The description of three methods of verifying " Py- 

 thagoras, " of four ways of measuring the weight 

 of a cubic centimetre of water, and of no fewer than 

 eleven experiments to show that air exerts pres- 

 sure indicates too much devotion to completeness 

 of detail at the expense of time which could be 

 spent more profitably in giving the pupils glimpses 

 at the marvels of Nature by which they are sur- 

 rounded. 



The Struggle in the Air, 1914-18. By Major 

 Charles C. Turner. Pp. viii4-288.. (London: 

 Edward Arnold, 1919.) Price 155. net. 

 Major Turner gives an extremely instructive and 

 readable account of the development of aircraft 

 from 1914 to 1918. With the work of a genera- 

 tion compressed into four years of war, it is not 

 surprising that the developments and events nar- 

 rated crowd upon each other in bewildering suc- 

 cession. The psychology of flying and the official 

 requirements as regards details of machines for 

 war purposes form exceptionally valuable chapters 

 of the book. 



Calculation of Electric Conductors. By William T. 

 Taylor. Pp. 34. (London: Constable and Co., 

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



A CHART supplied with the book enables the elec- 

 trical engineer to determine the size of a con- 

 ductor required to convey a current of a given 

 value when the voltage drop and length of cable 

 are given, or to find any of these quantities when 

 the three others are given. With the help of the 

 explanatory text all the ordinary cables and 

 systems can be thus dealt with. 



Revision Arithmetic, Logarithms, Slide Rule', Men- 

 suration, Specific Gravity, and Density. By 

 Terry Thomas. Second edition, revised. 

 Pp, 62. (London : Crosby Lockwood and Son, 

 1920.) Price 25. 6d. 



Numerical examples and answers are given, The 



standard is that of the Army and Navy Entrance 



Examinations. 



