﻿432 Notices respecting Sew Boohs. 



whereas in terms of the conductivity it is known to be 

 io-Eo 2 ; so that 



N* 2 Z A 



° = *\/l 



it mu. 



V 3tt mu l + J m 



ve~ v dv 



which is the result obtained on the more direct method 

 suggested by Thomson. For very long waves, it reduces, as 

 it should, to Lorentz's original formula. 



A full discussion of the actual bearing of these results on 

 the electron theory of the optical properties of metals will 

 be reserved for a future communication which is in course 

 of preparation. The main point of the present paper seemed 

 worthy of special and separate attention in the more general 

 theory rather than in the restricted branch of it which is 

 concerned with the optical properties only. 



The University^ Sheffield. 

 Nov. 4th; 1914. 



XL VII. Notices respecting New Books. 



Hie Electrical Conductivity and Ionization Constants of Organic 

 Compounds. By Heyward Scudder. Constable & Co., 1914. 

 12s. nett. 



r |\HIS is a bibliography, extending to 563 pages, of the peri 

 ■*■ literature from 1889 to 1910, inclusive, including all imp< 



-iodical 

 important 



work before 1889 and corrected to the beginning of 1913, and gives 

 numerical data for the ionization constants at all temperatures at 

 which they have been measured and some numerical data of the 

 electrical conductivity. The compilation thus deals with all the 

 important work on the ionization constants and the electrical 

 conductivity of organic compounds from the commencement up to 

 the year 1910, at which date the Tables Annuelles International 

 de Constants et Donne'es Numeriques begin. The book con- 

 stitutes in its somewhat limited field a useful work of reference to 

 those engaged in the subject. But unless it should prove in the 

 future of value as a starting point in the comprehensive reexami- 

 nation of the whole question from a theoretical standpoint, it may 

 be doubted whether such a great expenditure of time and labour 

 as the work has entailed has been profitably undertaken. 



