NA TURE 



505 



THURSDAY, SEPTEMBER 24, 190S. 



RADIO-TELEGRAPHY. 



Radio-Telegraphy. By C. C. F. Monckton. Pp. 



xvii + 272. (London: A. Constable and Co., Ltd., 



igoS.) Price 6s. net. 

 /^NE of the greatest triumphs of the school of 

 ^^ philosophy founded by Bacon is, doubtless, the 

 discovery and theoretical and experimental development 

 of electromagnetic oscillations. In this, as in most 

 other matters in the science of electricity, the founda- 

 tion stone was laid by Faraday, in his conception that 

 the medium between electrically charged bodies, and 

 between bodies carrying electric currents, was the seat 

 of the strains and stresses set up by the said electrical 

 disturbances. The subsequent development is, now- 

 adays, common knowledge. It will suffice to refer 

 simply to Maxwell's mathematical formulation, in 1873, 

 of Faraday's conceptions, and the hypothesis that the 

 electromagnetic strains in the medium travelled at a 

 definite speed, depending on the permeability and 

 specific inductive capacity of the medium. 



The next great step forward was the brilliant experi- 

 mental demonstration of electromagnetic waves which 

 Hertz made about the year 1890. There is no doubt 

 that Hertz was the true discoverer of radio-telegraphy. 

 True it is that the range of his transmission was only 

 a few yards; nevertheless, he was the first man to 

 transmit signals over a distance by means of electro- 

 magnetic waves. Hertz, however, worked for science 

 and not for telegraphy, and it remained for a host 

 of inventors to adapt the newly-discovered phenomena 

 to practical use. Prominent among these latter is the 

 name of Marconi. The great achievement made by 

 him was in 1896, when, experimenting for the British 

 Post Office, he constructed his oscillator, or transmitter, 

 by carrying a conducting wire high into the air as one 

 arm, whilst he connected the other arm to earth. 



Since then a large number of improvements and de- 

 velopments have been made under Marconi's auspices, 

 and this country certainly owes him its thanks for the 

 energy and perseverance which he has put into push- 

 ing forward into practical use what is certainly one of 

 the greatest applications of modern science. However, 

 very many other eminent inventors and men of science 

 have done a vast amount of work in bringing this new 

 industry to its present state of relative perfection. 

 Among these should be mentioned Lodge, Braun, de 

 Forest, Muirhead, Fessenden, Fleming, Slabv, Arco, 

 and others. One of the most recent, and what will 

 probably be one of the most important, steps forward 

 has been taken by Poulsen. In the musical arc 

 Duddell had utilised the earlier discovery of Elihu 

 Thomson, that electric oscillations could be produced 

 bv shunting an air gap in a continuous current cir- 

 cuit, with capacity and inductance, and he was thus 

 able to produce frequencies of 50,000 per second, which 

 were, however, too low to admit of radiation. Poulsen, 

 by using an arc struck between carbon and copper elec- 

 trodes, in an atmosphere of hydrogen, has obtained 

 frequencies of 1,000,000 per second, and thus the possi- 

 NO. 2030, VOL. 78] 



bility of radiating into space a continuous undamped 

 train of waves has been attained. 



As was, perhaps, not unexpected, the commercial 

 exploitation of an industry developing at the- rate 

 this is doing has been attended with a. certain amount 

 of friction and recrimination. A short time ago 

 it seemed possible that progress might be pre- 

 vented by a radiotelegraphic war, due to the com- 

 mercial rivalry between the Marconi and the com- 

 bined German interests. Fortunately, however, the 

 GOTernments of all the principal countries of the 

 world have made a satisfactory agreement which 

 came into operation on July i of this year. One 

 of the things which the conference of 1906 did, and 

 which will appeal perhaps to the man in the street, is 

 that they standardised the name of the new method 

 of communication, the official designation of the new 

 system being that used as the title of this book. 



Mr. Monckton is to be congratulated on having 

 written a very interesting and valuable book, and 

 the publishers likewise on the good style in which 

 it is produced, and on the many excellent illustrations. 

 The book contains a general exposition of the prin- 

 ciples underlying the subject, together with a descrip- 

 tion of a large amount of the apparatus and methods 

 used by the various companies. We would like speci- 

 ally to felicitate the author on chapters ii., iii., and 

 iv., where, without the use of mathematics, he has 

 given a really brilliant description of the properties 

 of electric waves. 



Authors of such books as this have a natural desire 

 to start right at the beginning of their subject, and, as 

 Mr. Monckton is not an exception to this rule, he has 

 devoted chapter i. to an explanation of the elementary 

 principles of electricity and magnetism. We are 

 rather afraid that if an absolute layman were to take 

 up the book his understanding of the same would 

 not be greatly helped bv this first chapter. Never- 

 theless, it serves as an appropriate introduction to 

 the volume, and will perhaps be useful to those en- 

 gineering readers whose elementary scientific ideas are 

 apt to get a little rusty in the rush of modern busi- 

 ness. In fact, w^e think this book will especially 

 appeal to those engineers and scientific workers who 

 are busilv engaged upon some other branch of the 

 profession, and yet laudably desire to know what 

 progress this young and very lusty addition to the 

 faniily of industrial applications of science is making. 



To conclude this notice, reference must be made to 

 chapter x., which deals with measurements in radio- 

 telegraphy. It is a commonplace remark that electri- 

 city is a science of exact measurements. With the 

 advent of radiotelegraphy it was found that hardly any 

 of the instruments hitherto used were suitable for mak- 

 ing measurements of the very high-frequency currents 

 used. As a consequence, a considerable number of 

 very ingenious instruments has been invented. The 

 principles underlying many of the measurements, for 

 example, of that all-important one— the measurement 

 of wave-length — are identical. The measuring instru- 

 ment consists of a circuit of variable self-induction 

 and capacity. It is brought under the electric influ- 

 ence of the circuit to be tested, and by varying the 



Y 



