320 Notices respecting New Books. 



ebonite, so that it would get a charge on the side next the 

 fixed sector equal and opposite to that induced on the moving 

 sectors. Consequently the total charge on the disk would be 

 zero, and so no magnetic field would be produced. 

 I am, Gentlemen, 



Your obedient Servant, 



Harold A. Wilson. 



XXXI. Notices respecting New Books. 



Rapports Presenles au Coiigrbs International de Physique, 1900. 



^assembles et publies p;ir Ch.-Ed. Gtjillaume et L. Poincare, 



Secretaires generaux du Congres. Paris : Gauthier-Villars, 1901 . 



Tome I. pp. xvi + 698; Tome II. pp. 570 ; Tome III. pp. 620. 

 rpiLE dawn of a new century forms a fitting occasion for retrospects. 

 -*■ Of such retrospects we have had abundance, but surely few 

 subjects can be considered more appropriate to the occasion than 

 the scientific progress which undoubtedly forms the most striking 

 characteristic of the century which we have just left behind us. 

 The extraordinary, almost miraculous spread of the spirit of 

 scientific inquiry, and the consequent rapid advance of science, 

 are not only unparalleled in the world's history, but constitute a 

 development which nobody at the commencement of the 19th 

 century would probably have been bold enough to predict. We 

 have been advancing by leaps and bounds, until at the beginning 

 of the new century we find ourselves in the possession of know- 

 ledge, and means of applying that knowledge to practical ends, 

 which far transcend the wildest dreams of enthusiasts in bygone 

 ages. 



It was therefore a peculiarly happy suggestion on the part of the 

 organisation committee of the first International Physical Congress 

 held at Paris in connexion with the 1900 Exhibition, that the 

 occasion of its meeting should be rendered memorable by the 

 publication of a work of more than passing interest — a sort of 

 resume of the state of physical knov\ ledge up to the end of the 

 nineteenth century. In order to obtain trustworthy and authori- 

 tative accounts, the committee invited the co-operation of a number 

 of eminent specialists in various branches of physics. The results 

 of this effort are embodied in the three volumes before us, and it 

 must be confessed that, so far as physical science is concerned, no 

 more valuable or interesting mode of commemorating the close of 

 the nineteenth century could have been found. 



Vol. I. deals with General and Molecular Physics, and opens 

 with a most interesting paper by M. H. Poincare " On the Relations 

 between Experimental aud Mathematical Physics." The subjects 

 which are discussed in this volume are : standards of length, 

 national physical laboratories, thermometric scales, pyrometrv, 

 dynamical equivalent of heat, specific heat of water, velocity of 

 sound, Bjerknes's theory of hydrodynamic actions-at-a- distance, 



