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NATURE 



271 



THURSDAY, JANUARY 6, 1910. 



THE ETHER OF SPACE. 

 The Ether of Space. By Sir Oliver Lodge, F.R.S. 

 Pp. xvi + 156. (London: Harper and Bros., igog.) 

 Price 2s. 6d. net. 



T^HIS book is a contribution to what the publishers 

 -1- describe as a '• Library of Living Thought." In 

 appealing to Sir Oliver Lodge for a book on the ether 

 they could count on getting something which could 

 certainly be called " thought," in the most exalted 

 sense of the word, and would as certainly be alive. 

 But, notwithstanding the many picturesque images 

 with which the theme is illustrated, we must confess 

 that we have found the book as a whole somewhat 

 unsatisfactory. This is perhaps due to a certain in- 

 definiteness of aim; some sections would seem to be 

 addressed to the cultivated dilettante, and dwell at 

 great length on very elementary matters, whilst others 

 can hardly be appreciated except by the expert who is 

 already conversant with the more abstruse parts of 

 electrical and optical theory. Thus the primary 

 notions of aberration are expounded very fully, whilst 

 the theories of Michelson's experiments and of 

 Fresnel's law of wave-velocity in a moving substance 

 are treated with tantalising brevity. Again, the 

 mechanical and optical details of the author's own 

 experiments with the "etfier machine" are given with 

 a minuteness which in a work on the present scale 

 rather tends to distract attention from the main point. 

 The ether has in its not very lengthy history under- 

 gone many transformations. The unsatisfactory 

 elastic-solid medium of the last century, with its 

 abundant provision for the explanation of non-existent 

 phenomena, has at length gone, to the general relief. 

 But the newer ether which is gradually being evolved 

 in its place, with its ability to exercise force, and, at 

 the same time, its utter indifference to forces exerted 

 on itself, appears somewhat shadowy and mysterious. 

 When the conceptions are resolved into their elements 

 we are left with little more than what the mathe- 

 maticians call a "vector-field." It might seem, indeed, 

 that the physicist had only to take one step more, and 

 hand over the whole medium, as a pure abstraction, to 

 the mathematician, who, for his part, is disposed to 

 welcome the gift with enthusiasm as affording, after 

 a few improvements, an unexpected outlet for the 

 theory of groups. His one regret is that he did not 

 (as he confesses he ought to have done) invent the 

 whole thing for himself. 



Sir Oliver Lodge, like Lorentz, comes to the brink, 

 lut he will not take the plunge. The most interesting 

 parts of this book are those in which he explains the 

 lengths to which he is prepared to go in the effort to 

 retain a mechanical basis for phenomena. He admits, 

 indeed, that ordinary matter is an imposture, but he 

 clings resolutely to something very real and very 

 substantial in the background. He reproduces 

 his recent arguments to show that if the 

 inertia of the atoms of ordinary matter is merely 

 the manifestation of that of a surrounding medium, 

 the density which it is necessary to attribute to the 

 NO. 2097, ^'Ot. 82] 



latter is something like 10'- that of water. This 

 seems at first sight like a nightmare, but it is in no 

 sense incredible. Waiving details which can have no 

 great influence on the result, it is, indeed, from the 

 author's point of view, mathematically incontestable. 

 He goes on to speculate on the origin of the forces 

 which this medium can exert. Assuming a kinetic 

 theory of force as the only one ultimately acceptable, 

 he sums up his conclusions in a sort of anthem : — 



" Every cubic millimetre of the universal ether of 

 space must possess the equivalent of a thousand tons, 

 and every part of it must be squirming internally with 

 the velocity of light." 



It will be seen that the book is in substance a re- 

 statement of the author's most recent speculations, in 

 which, of course, he stands by no means alone. If 

 it somehow fails to do full justice to these, and if in 

 some respects the original papers in the Philosophical 

 Magazine and elsewhere will probably be found by 

 many to be really easier reading, the auspices under 

 which it is brought out are no doubt partly account- 

 able. The general reader, even if he is disposed to 

 take most things on trust, and does not adopt the 

 critical attitude which the author -would himself 

 welcome, will at all events learn to understand the 

 admiration which the scientific world feels for the 

 genius and unflagging spirit with which a most 

 difficult as well as stupendous theme is repeatedly 

 essayed. H. L. 



NEW METHODS OF WEATHER FORECASTING. 

 Nouvelle Methode de Prevision du Temps. By Gabriel 



Guilbert. Pp. xxxviii + 343. (Paris: Gauthier- 



Villars, 1909.) 



MONSIEUR GABRIEL GUILBERT, the winner 

 of the prize offered in 1905 by the Soci^te beige 

 d'Astronomie, de Meteorologie et de Physique du 

 Globe, for the most successful short-period forecasts of 

 weather, has published in book-form a detailed exposi- 

 tion of the principles underlying his method. He 

 introduces two new principles into the art of weather 

 forecasting, which, so far as we are aware, have not 

 been stated explicitly by any other writer on this 

 subject. First, he invites us to compare the force 

 of the wind at the surface as observed at the various 

 stations contributing to our daily weather reports with 

 the barometric gradient at sea-level. If in any region 

 the observed wind forces are markedly in excess of the 

 normal for the prevailing gradient, a surge of high 

 pressure in the direction of the gradient may be 

 looked for, and vice I'cr.s.i. His definition of the 

 word "normal" is entirely conventional. It is based 

 on comparisons made by Clement Ley, Sprung, 

 Koppen, and others, and is that the number expressing 

 the wind force on the Beaufort scale shall be twice 

 that expressing the gradient in millimetres of mercury 

 per degree (in km.). It follows from this general 

 principle that a depression which is surrounded on all 

 sides by winds in excess of the normal will fill up, 

 whereas a depression surrounded by winds in defect 

 will grow deeper. If the defect is great, a depression 

 of small intensity will develop into a violent storm 



