January 13, 192 ij 



NATURE 



that for X-ray work the condenser capacity should 

 be as small as is consistent with preventing undue 

 sparking at the interrupter ; and he has grown to 

 realise that the design and performance of the 

 interrupter are all-important and may enhance 

 or undo his work on the coil. 



There are certain other features which the 

 • oil-maker has learnt to incorporate in his 

 design. He allows for each kilo-volt-ampere 

 input about 15 lb. of iron core, of which he 

 makes the length from six to ten times the 

 diameter. He winds the primary so as almost 

 to cover the whole length of the core, but he 

 keeps the length of the secondary down to about 

 three-quarters the length of the core, and finds 

 that the diameter of the secondary should not 

 <xceed about 25 times its bore. .Among many 

 other guiding facts, he estimates to get about 

 4 kilo-volts from every 1000 turns in the second- 

 ary, knowing also that a transformation ratio in 

 the region of 100 to 1 is a practicable figure. 



All this and much besides is to be found in 

 Mr. Codd's book. He supports many of his con- 

 tentions with the help of a large number of oscil- 

 lograph records. W'e regret to find no mention 

 it Prof. Taylor Jones's work, but we gather that 

 I he book is limited to the author's own experi- 

 I nee. There is a useful bibliography, but no 

 index. 



Our Bookshelf. 



'I'hc Romance of the Microscope. By C. A. Ealand. 

 Pp. 314. (London: Seeley, Service, and Co., 

 Ltd., 1921.) Price js. hd. net. 



To the well-known "Library of Kfimance " Mr. 

 C. .A. Ealand contributes a volume on the micro- 

 scope. He gives a glimpse of the early days of 

 invention, of pioneer microscopists such as 

 Leeuwcnhoek and Hooke, and of the principles 

 of the instrument. He then illustrates the use of 

 the microscope in studying the life of ponds and 

 streams (but why call the amcrba "a free swim- 

 ming denizen"?), the structure of plants, the 

 structure of animals (in the course of this investi- 

 gation, " Having taken our fill of the spiders' feet 

 we may well turn our attention to their heads "), 

 .sections of r(x;ks, impurities of food, bacteria, 

 blood, rusts on leaves, small insects and parts of 

 in.sects, and so on. We are sometimes forced to 

 doubt the author's sincerity, as when he says 

 that if we put the liver-fluke under the microscope 

 "we can plainly sec all its internal organs." That 

 ha.s not been our experience, nor anyone's. Simi- 

 larly, wc are not pleasantly impressed by being 

 told that Deniodvx foUiculorum (or, as the author 

 has his specific names printed throughout. Demo- 

 dcx FoUiculorum) is to Ix- found in the sweat- 

 glands. The l)o<»k ends with more practical 

 matters : the micro-telescope and super-microscope, 



(. NO. 2672, VOL, ro6] 



chemistry and the microscope, the use of the 

 microscope in manufacture, the camera and the 

 microscope in alliance, the glass used in making 

 len.ses, and the choice and use of apparatus. 



We think the book will help to diffuse an in- 

 terest in microscopy, which, of course, means the 

 discovery of a new world and of a new joy in lifei 

 but we wish the author had shown more micro- 

 .scopic precision in his workmanship. He tells us 

 that, having found our sea-slug or sea-cucumber, 

 especially the species called Syiiapta Inhaerens, 

 we find by touch that its leathery skin is studded 

 with .some flinty matter, which we go on to verify 

 under a low magnification. .And so passim. 



Organic Chemistry for Advanced Students. By 

 Prof. Julius B. Cohen. Third edition. Part i., 

 Reactions. Pp. viii-t-366. Part ii.. Structure. 

 Pp. vii-f 435. Part iii., Synthesis. Pp. vii + 378. 

 (London : Edward .Arnold, 1920.) Price 18s. net 

 each volume. 



That a reprint of the above work should be called 

 for in just over a year after the publication of the 

 last edition is clear evidence, if such were needed, 

 of the value of the book ; it may further be taken 

 as welcome proof that there exists a large circle 

 of serious students who are not content to acquire 

 their knowledge in "tabloid form," but arc pre- 

 pared to work through a three-volume treatise 

 on advanced organic chemistry. The book has an 

 important mission to fulfil in imparting a sound 

 knowledge of the principles underlying the modern 

 developments of organic chemistry to the rising 

 generation of chemists, and, from the rapid ex- 

 haustion of the last edition, one may conclude 

 that it is successfully accomplishing this. 



The present edition calls for little detailed com- 

 ment, since no material changes have been made 

 in the text, the author having confined himself to 

 adding a number of references to recent literature, 

 which will enable the student to bring his informa- 

 tion up to date. 



Leicestershire. By (i. \. PingrifT. Pp. xii-(-i64. 

 (Cambridge : ,At the University Press, 1920.) 

 Price 4s. 6d. net. 



An interesting description of the many features 

 of interest in Leicestershire is given in this book 

 by pen and photograph. In the opening chapters 

 the position, general features, rivers, and water- 

 sheds of the county are described. Its geology, 

 natural history, and an account of its climatic con- 

 ditions follow. Four chapters are then devoted 

 to the people of Leicestershire and their indus- 

 tries, stress being laid on the increase of grass- 

 land as opposed to arable farming. The remainder 

 of the book deals with the history and antiquities 

 of the county, and the concluding chapter is a 

 useful index to its chief towns and villages. In- 

 structive diagrams, showing graphically the pro- 

 portions of the acreage of the principal crops, form 

 a brief appendix. The b<K>k is throughout well 

 illustrated by interesting photographs and sketch- 

 maps. 



