240 



NATURE 



[August 24, 191 1 



face absorption of the wave makes it almost impos- 

 sible to check the mathematical theory which has 

 been given. 



(2) The second book before us for review is a third 

 edition of Dr. Erskine-Murray's well-known " Hand- 

 book of Wireless Telegraphy." The present edition 

 contains a considerable amount of new matter, but 

 the explanations given of fundamental effects, such 

 as the creation of Hertzian waves, are somewhat too 

 brief to be very useful. The student is not much 

 assisted merely by reproducing on a double page 

 Hertz's well-known diagrams of the electric radiation 

 of a dumbbell oscillator accompanied onlv by an extract 

 from Hertz's own book, and without further elucida- 

 tion of the difficulties involved. Rather too much 

 space is occupied in some parts by extracts from 

 original papers, whereas the essentially new informa- 

 tion could be concentrated and difficulties removed by 

 a more independent authorship. 



After the usual introductory chapters dealing with 

 early history, three chapters follow on detectors for 

 electric waves, considerable space being given to the 

 theory of magnetic detectors and descriptions of 

 forms which have not been much used for radiotele- 

 graphy, whilst the contact or rectifying detectors 

 are very briefly treated. With regard to Fleming's 

 glow-lamp detector, the erroneous remark is made 

 that Dr. de Forest " improved this detector." As 

 a matter of fact, his improvements did not enable 

 it to operate better than in its original form. 

 Chapters viii., ix., x., xi., and xiii. are devoted to 

 descriptions of the Marconi, Lodge-Muirhead, Fessen- 

 den, Hozier-Brown, de Forest, and Telefunken "sys- 

 tems " of wireless telegraphy. All of them, however, 

 involve essentially the same system, viz. the spark 

 method, and differ only in the details of the apparatus 

 used. A chapter, which is, however, interesting, is 

 given to methods and apparatus which have never 

 reached the practically efficient stage, such as the 

 "world wave telegraphy" described in chapter xviii., 

 in which Tesla's somewhat tentative experiments are 

 discussed. There is no evidence that any useful tele- 

 graphic work has been carried out by these methods. 



In the chapter on theories of transmission, a 

 large amount of information is collected on the 

 influence of atmospheric states on radiotelegraphic 

 transmission. Facts are being accumulated which 

 seem to connect variations in received signals over 

 long distances with changes in atmospheric electricity. 

 Much work has yet to be done before a satisfactory 

 theory can be evolved, and it is therefore perhaps 

 premature to attempt to construct such theories in 

 text-books issued now. For one thing, we need much 

 more information than we now possess as to the 

 variation in atmospheric conductivity at high eleva- 

 tions, which may some day perhaps be provided by 

 the use of dirigibles or aeroplanes. 



Dr. Murray's book concludes with a useful chapter 

 on high-frequency electric measurements and appen- 

 dices containing many valuable practical tables, 

 curves, and memoranda. The book is well printed and 

 fully illustrated, and certainly one to be included in 

 any radiotelegraphic library. J. A. F. 



NO. 2l82, VOL. 8/] 



THE SCIENCE OF SHIPBUILDING. 

 The Design and Construction of Ships. By Prof. 

 J. H. Biles. Vol. ii., Stability, Resistance, Pro- 

 pulsion, and Oscillations of Ships. Pp. x + 428. 

 (London: C. Griffin and Co., Ltd., 1911.) Price 

 255. net. 



THIS second volume was originally intended to 

 complete the work, but the author found his 

 materials growing rapidly and wisely decided to de- 

 velop more fully in a third volume his treatment of 

 ship-designing. Like the first volume — reviewed in 

 Nature, February iS, 1909 — the second is complete in 

 itself. It will be of much value as a text-book for 

 advanced students of naval architecture, and as a book 

 of reference for men engaged on the practical details 

 of ship-design. The contents are arranged in four sec- 

 tions; in which the stability, resistance, propulsion, and 

 oscillations of ships are discussed. Under each head 

 is presented an excellent r&sum& of the accepted theory 

 of the subjects treated ; in association with valuable 

 data, drawn from recent practice, illustrating the 

 characteristics of various types of ships. A mass of 

 information which was previously widely scattered in 

 various publications has thus been concentrated, in- 

 cluding published results of the latest experimental 

 research work. 



In dealing with the geometric theory of stability the 

 author has naturally followed the lines laid down by 

 M. Charles Dupin in his memoir entitled " Stability 

 des Corps Flottants " (published in 18 14), one of the 

 series of " Applications de G^ometrie " presented to the 

 Institute of France. Dupin for all practical purposes 

 exhausted the subject, although certain corrections 

 and extensions of his generalisations have since been 

 made by other investigators, more especially as the 

 result of determinations by calculation and experiment 

 of the stability of actual ships made during the last 

 forty years. Prof. Biles describes the methods of cal- 

 culation, as well as the ingenious integrating instru- 

 ments (devised by Amsler and others) by means of 

 which arithmetic labour has been greatly reduced. 

 Typical examples are given of curves of stability con- 

 structed for many classes of ships, and for different 

 conditions of lading; and the whole section has been 

 arranged in a manner which will enable advanced 

 students to master present knowledge of the subject, 

 while draughtsmen and others who are engaged in the 

 work of calculations of stability will find help and 

 guidance. 



From the middle of the eighteenth century mathe- 

 maticians and experimentalists have been attempting 

 general solutions of the problems of water-resistance 

 to the motion of ships, but with moderate success, and 

 with small practical influence on ship-design, until the 

 late William Froude, little more than forty years ago, 

 introduced the system of experiments on models. 

 Froude demonstrated the law of comparison between 

 ships and models moving at "corresponding speeds," 

 and showed how to make the necessary correction for 

 frictional resistance when passing from models to 

 ships. Model experiments are now universally re- 

 garded as necessary to successful steamship design, 



