REVIEWS 581 



The Wonders of Wireles3 Telegraphy. By H. A. Fleming, M.A., D.Sc, 

 F.R.S. [Pp. xi + 279.] (London : Society for Promoting Christian Know- 

 ledge, 1913- Price y. 6d.) 



There are very few scientific men of eminence who have the gift of making the most 

 abstruse subjects clear and interesting to the multitude. Prof. Fleming is happily 

 one of these, and his little book on the Wonders of Wireless Telegraphy is not 

 only a model of clear exposition, but is an example of how to select and arrange 

 just the features of interest which the ordinary reader desires to hear about. If 

 we add to these points yet one more, and probably the most important of all, that 

 there is from cover to cover of the little book neither a loose statement nor an 

 unfounded assertion, and that there is nothing in the way of unsound popular 

 science, it is clear that this book may be warmly and heartily recommended 

 to readers young and old. 



The first chapter, dealing with the aether, electricity, and electrons, commences 

 with a brief account of what we know of the aether itself, treating historically the 

 different steps in the discovery of the velocity of light, and putting clearly and 

 concisely the electrical and optical phenomena which science helps us to under- 

 stand, and a knowledge of which is the first step in a study of the nature of the 

 aether itself. An interesting and popular account is given of the researches of 

 Thomson, Rutherford, Soddy, and M. and Madame Curie. Having given an 

 outline of the constitution and structure attributed to the universal space-filling 

 aether, and the way in which the electricity atoms are now supposed to be built 

 up from it, the next step is naturally to discuss electric waves and oscillations, 

 and the second chapter deals with these oscillations, making use of the hypothesis 

 of the lines of strain or lines of force, and the electrons or strain forms or centres 

 from which twists or waves in aether start. In this chapter is clearly shown the 

 difference between damped intermittent oscillations and undamped oscillations, 

 and the way in which lines of electric force surround the Hertzian Oscillator. 



The third chapter deals with actual wireless telegraph instruments, and the 

 sending of wireless messages ; but the author leads up to this important subject 

 by a description of signalling both in the Army and Navy, and continental practice 

 and mode generally, in which intelligence is transmitted at a distance by signals, 

 particularly the Morse Code, giving as prelude to wireless telegraphy the more 

 simple case of telegraphy in which wires are used. This is followed by a descrip- 

 tion of various types of antenna or aerial used with wireless telegraphy. Also a 

 special account is given of the Marconi discharges and arrangements for producing 

 persistent oscillations by the electric arc. 



The next chapter deals generally with the subject of force receivers as distin- 

 guished from transmitters, showing how connections are made with the receiving 

 circuits. It is explained how with a combination of a telephone in series with an 

 electrical valve a telephone can make audible the sparks of a transmitter hundreds 

 of miles away. 



The Marconi magnetic detector and coherer is described, and the author's 

 own cymometer. The two final chapters deal with wireless telegraphy over land 

 and sea, the transmission of wireless waves around the world, wireless telegraphy 

 and telephony in practice, and the utilisation of electromagnetic waves. 



It may be remarked— and this is a matter of no small importance — that the 

 illustrations of the book throughout are excellent ; and the diagrammatic figures, 

 many if not most of which are new, tend to make the descriptions of the text 

 admirably clear. 



