510 Notices respecting New Books. 



A detailed theory of radiation pressure was developed by 

 K. Schwarzschild*, and published in 1901, in which, by 

 means o£ somewhat intricate mathematical analysis, he suc- 

 ceeded in arriving at numerical results, according to which 

 the radiation pressure on a spherical particle vanishes when 

 the radius is too small to include several wave-lengths of the 

 incident radiation. The investigation is, however, based on 

 Maxwell's equations of electric force, in which the existence 

 of the polarization current is not recognized, and is therefore 

 invalid. 



Dr. J. W. Nicholson, in his recent paper " On the Size of 

 the Tail-particles of Comets, and their Scattering Effect on 

 Sunlight "f, relies largely on Schwarzschild's results. The 

 writer was also referred to these results in December 1909, 

 by Prof. Svante Arrhenius, when kindly reading some of the 

 proofs of the work previously referred to, in which some 

 modifications had been made in the theory proposed by Prof. 

 Arrhenius to account for the constitution of the solar corona 

 and the origin of the polar auroras. It therefore appeared 

 advisable to draw attention to their unsoundness in a more 

 prominent way than has already been done in a footnote to 

 the writer's recent work J. 



LV. Notices respecting New Books. 



Mathematical and Physical Papers. Vol. IV. Hydrodynamics and 

 General Dynamics. By the Eight Honourable Sir "William 

 Thomson, Baron Kelvin. Arranged and Eevised with brief 

 annotations by Sir Joseph Larmor, D.Sc., LL.D., Sec. E.S. 

 Cambridge : at the University Press. 1910. 



HPWENTY years have elapsed since the Third Volume of Kelvin's 

 -*- collected papers was issued. During that period Kelvin 

 himself edited and greatly expanded the Baltimore Lectures, and 

 added many new papers to the already long list of original contri- 

 butions to science. But the remarkable papers on Vortex Motion 

 remained generally inaccessible save to students in command of a 

 good scientific library ; and many had to be content with the pre- 

 sentation of Kelvin's work as it was given in the Treatises of 

 Lamb and Basset. Now, thanks to the care and energy of 

 Sir Joseph Larmor, this has been changed. The present volume 



* Mimchencr Berichte, vol. xxxi. 1991, p. 293. 

 t Phil. Mag. vol. xix. 1910, p. 62G. 

 \ Op, cit. p. 378, 



