Notices respecting New Books. 553 



The results obtained by this method are given in the 

 following table : — 



No. of 

 experiment. 



v, 



v, 



in c.c. 



in c.c. 



360 



275 



36-95 



143 



29-6 



283 



22-9 



270-5 



26-2 



244 



54-3 



243 



24-0 



272 



318 



140-1 



in div./min. 



34-2 



27-0 



34'1 



53-0 



14-40 



44-9 



12-98 



42-9 



in div./min. 



37-1 



29-8 



30-7 



54-4 



14-06 



30-8 



11-22 



37-0 



t 



T 



in days. 



in days. 



10-60 



3-76 



6-81 



3-78 



12-79 



3-75 



13-00 



3-71 



11-94 



3-80 



10-00 



3-70 



13-96 



376 



7-16 



3-72 





3-75 



Each of the numbers marked in the columns i x and i 2 repre- 

 sents the mean of four readings, which never differed from 

 their mean value more than one per cent. The values i ± , i 2 , 

 given in the table are corrected for the natural leak, the 

 column i 2 also for any slight change of sensitiveness of the 

 electroscope. 



As it will be seen, the mean of all the experiments, 3*75 

 days, agrees very closely with the original value obtained by 

 Rutherford and Soddy, 3' 7 7 days. It may be interesting to 

 note that Dr. Bronson in this laboratory recently also deter- 

 mined the period of the radium emanation, using an electro- 

 meter steady-deflexion method. Two decay curves of the 

 emanation obtained by him gave the value of T = 3*71 and 

 3*73 days. It thus seems certain that the period of the 

 radium emanation is not longer than 3*80 days, and very 

 probable that it is in the neighbourhood of 3*75 days. 



In conclusion, I desire to express my sincerest thanks to 

 Professor Rutherford, at whose suggestion these experiments 

 were undertaken, for his valuable advice during the proo-ress 

 or this work. 



Macdonald Physics Building. 

 McGill University, Montreal, May 1907. 



LIV. Notices especting Neiv Boohs. 

 Stereochemistry. By A. W . Stewart, D.Sc. London : Longmans 



Greeu & Co. 1907. Pp. xx+583. 

 AX/'E welcome this latest addition to the excellent series at 

 ** present being issued by Messrs. Longmans under the 

 general title of " Text-Books of Physical Chemistry." The enor- 

 mous amount of research carried out during the last few years in 

 the particular branch of chemistry with which the present work 

 is concerned has rendered the publication of such a volume highly 

 desirable, and it is sure to prove extremely useful to all student's 



