38 



NATURE 



[January 12, 1922 



in the United States for the distribution of suit- 

 able anthelmintics and the conduct of anti- 

 hookworm campaigns within its borders. 

 Processes for the preparation of these drugs are 

 well-known, and the authors would be rendering 

 a further service to their colleagues if they would 

 add a section on anthelmintics when a new edition 

 of their book' is called for. 



The volurne is well produced, and contains a 

 number of useful diagrams of plant and a good 

 index. The proof-reading has been carefully 

 done, and printers' errors are commendably few. 



T. A. H. 



Some New Text-books on Radio - 

 telegraphy. 



(i) Wireless Telegraphy and Telephony: An Out- 

 line for Electrical Engineers and Others. By 

 L. B. Turner. Pp. xii+195 + 24 plates. (Cam- 

 bridge: At the University Press, 1921.) 

 205. net. 



(2) Thermionic Tubes in Radio-Telegraphy and 

 Telephony. By John Scott-Taggart. Pp. xxiii + 

 424. (London : The Wireless Press, Ltd., n.d.) 

 255. 



(3) Continuous Wave Wireless Telegraphy. By 

 Prof. W. H. Eccles. Part i. Pp. vii + 407. 

 (London: The Wireless Press, Ltd., n.d.) 255. 

 net. 



(4) Principles of Radio-Communication. By Prof. 

 J. H. Morecroft, assisted by A. Pinto and 

 W. A. Curry. Pp. x + 935. (New York: J. 

 Wiley and Sons, Inc. ; Lon4on : Chapman and 

 Hall, Ltd., 192 1.) 455. net. 



(i) TT is a pleasure to come across a technical 

 X book, like that by Mr. Turner, which 

 has the literary quaHties of clearness, life, and 

 continuity. In too many scientific text-books the 

 manner is as cold as the matter is dead and 

 already dissected; the parts are evident, but the 

 whole is left to the constructive imagination of 

 the reader. A book may be crammed with exact 

 information, and yet be so unreadable as to have 

 little value from the point of view of education. 

 Even quite a slight historical framework adds 

 human interest and may guide the student along 

 the course of thought which resulted in discovery, 

 and a text-book in which such a framework exists 

 is therefore much more educative than one which 

 merely states the physical facts, however accu- 

 rately. 



Unfortunately for the average student a .sound 

 knowledge of the mathematics of motion is re- 

 quired in the study of the production of high- 

 frequency currents on account of the large number 

 NO. 2724, VOL. 109] 



of variables involved, especially when the con- 

 verter is a thermionic valve or an arc. Again, 

 unfortunately, this branch of mathematics is 

 known, in spite of Newton, by the entirely un- 

 illuminating and indeed repellent name of "the 

 differential calculus." "Calculation by differ- 

 ences " does not suggest motion any more than 

 "bits of iron" would suggest a locomotive, and 

 it is doubtful if the would-be engineer realises 

 that in avoiding this unpleasantly named subject 

 as much as possible he is debarring himself from 

 the most interesting and useful branch of mathe- 

 matics. Could not mathematical teachers make 

 the learning of the laws of motion more interest- 

 ing than the study of geometry in the same ratio 

 as a kinema is more attractive than a photograph ? 



In the books under review mathematics are 

 freely used except in (2) Mr. Scott-Taggart 's 

 "Thermionic Tubes," which is quite an encyclo- 

 paedia of types and circuits, but does not enter 

 deeply into exact theory, although the graphical 

 explanations are very useful. Mr. Turner has the 

 happy knack of working his equations so natur- 

 ally into the text that the deductions which he 

 makes from them are almost self-evident, and 

 although his book contains only 190 pages, there 

 is but little that could be added with advantage 

 to the outline which he has set himself to give. 

 An interesting personal opinion is given on 

 p. II, where he says he can derive no satis- 

 faction from the usual semi-Hertzian diagram of 

 w'ave radiation over a conducting surface; but 

 why should Dr. Howe's model, in which an in- 

 verted conducting cone with its apex at the trans- 

 mitter is substituted for the upper atmosphere, be 

 any simpler? It merely evades the question of 

 where the lines go in space, and neglects the fact 

 that aircraft experiments indicate that their direc- 

 tions are probably such as are shown in the 

 Hertzian diagram. The expression of the 

 opinion, however, shows the perfect honesty with 

 which Mr. Turner treats his readers. 



The other books are different in scope and 

 style. (3) Dr. Eccles 's is a first volume only and 

 is devoted to the theory of electromagnetic induc- 

 tion and conduction on metallic circuits and 

 vacuum tubes ; both branches of the subject are 

 treated clearly and in great detail, and a sound 

 basis is laid for a thorough understanding of the 

 technical applications which will presumably form 

 the greater part of his second volume. 



(4) Few, if any, books on radio-telegraphy have 

 covered so many details of the subject as Prof. 

 Morecroft's " Principles of Radio-Communica- 

 tion," and there is little connected with the func- 

 tions of radio-gear which he does not touch upon. 



