390 Notices respecting New Boohs. 



r 2 can be calculated from the mean resistance according to 

 the formula 



, l + 2dr 



r *¥ ' 



where r is the mean radius, I the length, k the specific 

 conductivity of mercury at the temperature of the experiment, 

 /'the resistance of the capillary (found). The term 2dr is a 

 correction to the measured length I for the stream-lines at 

 the end of the capillary, the value of d being 0*082 (see 

 Jeans's Electricity and Magnetism, 1908, p. 347). 

 The values thus foand for the three tubes were : — 

 r' 1 (sq. mm.). r (mm.). 



Tube A 0*002304 0*04780 



,, B 0-004406 0*06637 



„ C 0*004192 0-06474 



The error in r 2 is probably *000002 sq. mm. A measure- 

 ment of r for tube C with a microscope and micrometer 

 eyepiece gave the value of *064 mm. 



The only difficulty which arises consists in keeping the 

 tubes clean and free from moisture. 



In conclusion I should like to express my thanks to 

 Mr. H. B. Hartley and Mr. D. H. Nagel for their kind 

 assistance and advice in these experiments which were begun 

 at the Balliol and Trinity College Laboratory, Oxford. 

 18 Grosvenor Street, W. 



XLY. Notices respecting New Books. 



Traite de Eadioactivite. By Mme. P. Curie. 

 Two Vols. Paris : G-authier-Villars, 1910. 



nnHE course in Radioactivity given by Mme. Curie at the Sorbonne 

 -*- forms the basis of these two volumes, and the thousand pages 

 they contain testify to the energy and thoroughness with which the 

 new science is being pursued in the country of its origin. When 

 Mme. Curie was appoiuted to the position left vacant by M. Curie's 

 untimely death, cut off in the flowing tide of their joint discovery, 

 probably most people imagined that the position, as regards 

 academic duties, was an honorary one, intended to secure to the 

 surviving partner the uninterrupted pursuit and completion of the 

 investigations on radium. How well and continuously the latter 

 object has been served is best known to those who follow most 

 closely the progress of the subject, but the appearance of this 

 work will dispel any illusion that may have been entertained as to 

 the duties of the Professor of Radioactivity at the Sorbonne. It 

 is evident that research and the training of investigators goes on 

 alongside of a full course of lectures covering completely and in detail 



