894 Notices respecting Neiv Boohs. 



of the " K " series in radium C of atomic weight 214 is 

 1*27 x 10 13 £. Chapman (Proc. Roy. Soc. lxxxvi. p. 439, 

 1912) has shown that the characteristic radiation of the " L " 

 series emitted by the heavier elements corresponds in pene- 

 trating power to the " K" type of radiation from an element 

 of atomic weight J (A — 48). The corresponding energy 

 to excite this characteristic radiation in radium C is 

 •190 x 10 13 <? ergs. It is of interest to note that these two 

 values do not differ much from the values deduced for E x 

 and E 3 . 



As I stated in my paper, the values of the velocities of the 

 different groups of homogeneous rays from a product must 

 be known with great accuracy before the correctness of snch 

 difference relations between the energies can be adequately 

 tested. It is of great importance to know accurately the 

 distribution of the /3 rays from active products both as regards 

 velocity and number, for it is only with the help of such data 

 that we can hope to explain the origin of the remarkable 

 complex /3 radiation from active substances and its connexion 

 with the y rays. 



E. RUTHERFOKD. 



University of Manchester. 

 Nov. 4, 1912. 



XCIX. Notices respecting JSeio Books. 



Gesammelte IVerJce Walther JRitz : CEuvres publiees par la Societe 

 Suisse de Physique. Paris : Gauthier- Villars, 1911. 



T^ALTHER RITZ was born in 1878atSion in Valais, and died 

 * » in 1909 at the age of thirty-one, after a brief but brilliant 

 career as physicist and mathematician. In this book of collected 

 papers, edited by Pierre Weiss, we have a fitting memorial of one 

 whose early death robbed the world of a great investigator. His 

 Inaugural Dissertation, Zur Theorie der Serienspehtren, presented 

 at Gottingen University in 1903, was immediately published in 

 the Annalen der Physih and brought its author into the front 

 rank. To find a reason for Balmer's law of frequencies in series 

 of spectral lines was a problem to which Ritz returned again and 

 again. He finally hit upon an electromagnetic mechanism iu 

 terms of which he was able to elucidate not only line-spectra, but 

 also banded spectra and the Zeeman Effect. In his new method 

 for solving differential equations in elasticity and potential he de- 

 veloped a valuable practical means of calculating to any required 

 approximation the numerical values involved in any particular 

 problem. Ritz also gave much atteution to the general problem 

 of electrodynamics and optics. In several papers he critically 

 examined the necessity for the existence of the aether, and gave 



