December i6, 1915" 



NATURE 



421 



The first chapter may be regarded as a sum- 

 mary of those parts of mathematics and mathe- 

 matical physics which are applied to wireless 

 telegraph problems in the author's larger treatise. 

 There is a brief exposition of differential and 

 integral calculus, of differential equations, of the 

 theory of the Argand diagram, and of vector 

 analysis, culminating in an explanation of the 

 more mathematical aspects of divergence, curl, 

 and vector potential, and in the derivation of 

 Poisson's equation and- Stokes's theorem. Later 

 this theory is applied in the orthodox way to 

 the formation of Maxwell's equations and to 

 the solution in the standard manner of the 

 Hertz oscillator problem. The second chapter 

 is more physical than the first, and deals 

 with the important subjects of units and 

 dimensions. 



Chapters iii. to vi. discuss the laboratory 

 physics of wireless telegraphy, attention being 

 paid especially to the derivation of the formulae 

 used in the electrical laboratory. For example, 

 there is a good and fairly full account of the 

 theory of certain bridge methods of measuring 

 inductance and capacity. Chapters ix. and x. 

 deal with the principles underlying the produc- 

 tion of electric waves, and contain the principal 

 formulae for the radiation from antennae. Simi- 

 larly the next chapter, on the reception of signals, 

 is devoted largely to principles, though contain- 

 ing some useful pages occupied with brief descrip- 

 tions of various detectors. From the list of detec- 

 tors the modern forms of the vacuum valve de- 

 tector and relay are all missing, although these 

 are playing so large a role in recent long-distance 

 triumphs in wireless telegraphy and telephony. 

 Chapter xi. begins the practical portion of the 

 work. In it are given the Morse code, some hints 

 on the management of storage cells, a couple of 

 Images on the management of wireless telegraph 

 apparatus, and a glossary of terms. Chapter xii. 

 concludes the book with about fifty pages of the 

 usual mathematical tables and eight pages of 

 tables of physical constants. The mathematical 

 tables are very beautifully printed, and contain 

 some improvements designed to make reference 

 rapid and easy. 



The most permanent impression left by the 



')Ook on the mind of the reviewer is that the 



luthor appears to entertain a very high opinion 



f the intellectual equipment of the wireless tele- 



;raphist and of his ambition to breathe the rarest 



itmosphere of the subject. In all probability the 



Dook will receive a warmer welcome from the 



n^Bdvanced students of electro-technics in our col- 



I^^Kges than from the class it is ostensibly written 



^B NO. 2407, VOL. 96] 



(2) This little book is a translation of one issued 

 tw6 or three years ago by the Paris Bureau of 

 Longitudes for enabling French nagivators, clock- 

 makers, and others requiring accurate time, to 

 make full use of the excellent series of radio- 

 telegraphic time signals sent daily from the Eiffel 

 Tower station. Since the Paris station is only 

 one of a projected international chain of time 

 stations, such a book as this is, or will be, useful 

 in other countries. 



The work begins with a clear description of the 

 apparatus needed by a person who wishes to 

 receive the time signals ; several types of ap- 

 paratus are, in fact, described, l^eginning with 

 the very simplest and closing with a fairly ela- 

 borate plant. It will be difficult to find anywhere 

 an explanation more helpful to the novice than 

 this. Then follows an account of the kinds of time 

 signals emitted from the Eiffel Tower, which 

 include morning and evening sets of signals in- 

 tended for navigators and horologists, and also 

 scientific signals which give, by an application 

 of the method of coincidences, the time accurate 

 to about i/ioo second. 



Of course, the war has put much of the work 

 of the Eiffel station out of joint ; for instance, the 

 meteorological signals described in this book are 

 not now transmitted as before, but no hint of this 

 fact is given in the book, which, though dated 

 1915, speaks as if everything were proceeding 

 normally everywhere. This failure to take 

 account of the effects of the war on wireless tele- 

 graph matters appears even in the translators' 

 appendices, in one of which it is stated that 

 English weather reports are issued daily by the 

 Admiralty from Whitehall and'Cleethorpes. The 

 writer of this review cannot affirm with finality 

 that such reports are not issued; no private in- 

 dividual is now allowed to possess " wireless " 

 apparatus to test the matter — but it is unlikely 

 that meteorological reports are sent broadcast at 

 this period. This fault is apparently the only 

 fault of the work, and it is here pointed out for 

 the sake of historical accuracy* 



THE STEAM ENGINE. 

 Steam Power. By Prof. W. E. Dalby. Pp. xvi 

 + 760. (London: Edward Arnold, 1915.) 

 21.9. net. 



IN this volume we have the most complete, the 

 most scientifically correct, and the most up- 

 to-date treatment of the problem of the generation 

 of steam and its utilisation for power purposes 

 which has ever been put at the disposal of the 

 engineer and the designer of power plants. 

 Although Sir J. A. Ewing in the latest edition 



