September 15, 192 1] 



NATURE 



79 



Our Bookshelf. 



The Journal of the Institute of Metals. Vol. 25. 

 ' No. I. 192 1. Edited by G. Shaw Scott. 

 Pp. xiv + 522 + 27 plates. (London: The 

 -Institute of Metals, 192 1.) 315. 6d. net. 

 The papers read before the spring meeting of 

 the Institute and contained in the present volume 

 include two contributions of outstanding im- 

 portance. One of these, by Mr. Moore and his 

 colleagues, describes observ-ations on the season 

 cracking of brass and other copper alloys. The 

 authors have had an opportunity of deahng with 

 an exceptionally large mass of material, and have 

 come to the conclusion that, chemical corrosion 

 plays a prominent part in the initiation of season 

 cracking. Their theoretical explanation assumes 

 the existence of an amorphous film between the 

 crystals. 



" The second paper is by Prof. Carpenter and 

 Miss Elam, and describes the process of recrystal- 

 lisation of sheet aluminium on annealing, carrying 

 much further the previous observations of the 

 same authors. They have been able to show that 

 the confused structures which have been described 

 as characteristic of cold-worked aluminium are 

 the result of imp>erfect polishing and etching, and 

 that well-defined structures may be obtained even 

 in severely strained metal. Dr. Haughton has 

 continued his study of the copper-tin alloys and 

 has defined the limits of the solid solutions at the 

 tin end of the series, obtaining, however, some 

 curious results in the variation of the electrical 

 resistance with temperature. 



Prof. Edwards and Mr. Herbert describe ex- 

 I periments on the plastic behaviour of heated 

 ! copper alloys, employing an impact indentation 

 test. Messrs. Moore and Beckinsale have re- 

 investigated the action of reducing gases on 

 copper. Mr. P. H. Brace gives a general account 

 I of the metallurgy of calcium, about which little 

 is to be found in the literature. The abstracts of 

 metallurgical pap>ers are very numerous and full, 

 so that the volume constitutes an indispensable 

 work of reference on all matters concerning the 

 non-ferrous metals. Mention should be made 

 of the excellence of the illustrations. 



C. H. D. 



Freshwater Fishes and How to Identify Them. 

 By Dr. S. C. Johnson and W. B. Johnson. 

 Pp. 64. (London : The Epworth Press : 

 J. Alfred Sharp, n.d.) 15. gd. net. 

 A BOOK that is both cheap and easy to carry in 

 the coat pocket has long been wanted by those 

 who wish to identify our freshwater fishes. This 

 little volume meets their needs. The descriptions 

 are clear and accurate, and are concerned only 

 with external features, w^hile the majority of the 

 illustrations are in themselves sufficient for identi- 

 fication without reference to the letterpress. The 

 authors' style is not always above reproach; 

 nor do we fathom the meaning of "The 

 sturgeon Is considered to be a link between 

 true fishes and sharks, as it has gills as 

 XO. 2707, VOL. 108] 



fishes have, and a breathing spiracle, as 

 sharks have." Is it that the authors do npt 

 regard sharks as "true fishes"; and if noti' why 

 not? The usefulness of all books of this type 

 depends largely upon the ease and speed with 

 which the unknown catch can be run to earth and 

 identified ; and we have yet to learn that there 

 is anything better for this purpose than a di- 

 chotomous "key." We miss any such key in 

 these pages, and would therefore urge the authors 

 to endeavour in any subsequent edition to intro- 

 duce a "key" which can be applied rapidly in 

 the field. It would also improve the book if 

 dimensions were consistently introduced into the 

 description of each species : we are told that the 

 gudgeon is usually 5 or 6 in. long when full 

 grown; the "record" chub, how-ever, weighed 

 7 lb. 4 oz., but no hint of length is given; of the 

 barbel we are given neither the weight nor the 

 length— and so on all through. Nevertheless the 

 book will be welcome to many, and may easily be 

 made so to more. O, H. L. 



Agricultural Economics. By Prof. J. E. Boyle. 

 (Lippincott's College Texts : Agriculture.) 

 Pp. ix-r448. (Philadelphia, London, Chicago: 

 J. B. Lippincott Co., 1921.J 125. 6d. net. 

 Prof. Boyle's book covers a wide field and deals 

 with a subject of increasing importance. It has 

 long been a commonplace that agriculture is a 

 busmess as well as a science, but only recently 

 have the business principles been clearly enun- 

 ciated and developed. The book is a useful con- 

 tribution ; the author's position as professor of 

 rural economy at Cornell University brings him 

 in contact with the realities of the subject and 

 saves the work from the danger of becoming 

 commonplace. The author has a good deal to say 

 about the chaos that sometimes seems to reign 

 supreme in agriculture, but we are not sure that 

 it really is as bad as it appears ; prior to the war 

 the world's supply was on the whole approxi- 

 mately equal to the demand, and no great "carry- 

 over " was necessary, nor was there a marked 

 deficit. He is on safe ground, however, in insist- 

 ing on the need for the full co-ordination of pro- 

 duction and consumption, and his discussion of 

 the factors concerned in successful business man- 

 agement is both interesting and suggestive. 



The Child's Path to Freedom. By Xorman 

 MacMunn. A second edition, entirely re- 

 written, of A Path to Freedom in the School, 

 dealing with six further years of educational 

 experiment. Pp. 163. (London : G. Bell and 

 Sons, Ltd., 192 1.) 25. 6d. net. 

 This stimulating and original book deserves to 

 be studied carefully by every educator, for it 

 illustrates well the value of the application of 

 modern psychology to the problems of mental 

 development. There is much in it which will be 

 actively criticised, but it is well to have educa- 

 tional orthodoxy challenged to defend itself or to 

 modify its procedure, as is done in the pages of 

 this little volume. 



