the Constant of Uranium X. 



849 



All three preparations (D covered with zinc) were measured 

 from the start, so that the ratio of one to any other was 

 accurately known. When JB had decayed too much C was 

 continued in its place, then D covered with zinc, and finally 

 D bare. From these results Curve III. (fig. 1) was obtained. 

 The separate results are shown in Nos. 3, 4, 5 of Table I. 

 Of the preparation B of first separation (No. 1) only two 

 measurements were taken, one just after preparation, and 

 the other after the lapse of 236 days, so that this value of \ 

 is not of so much importance as the other values. The mean 

 value may be taken as 00282, and the maximum departure 

 in any single set of observations is less than 3 per cent. 



Table II. — Decay of y-Rays. 



No. 



Preparation. 



Days under 

 observation. 



A (day) \ 



1 







A (3rd Separation) 

 B (ditto) 

 C (ditto) 

 ABC (ditto) together 

 A (4th Separation) 



to 69-5 

 to 69-5 

 to 69-5 

 69-5 to 226 

 to 143 



00281 

 0-0280 

 0-0280 

 0-0281 

 0-0284 



3 



4 



5 





Fig. 2. 



15 



13 30 to qo 



Nos. 1 to 4, and 5 are plotted in Curves I. a 

 The mean value of X (day) : obtained for the y-rays is 0*0282, 



210 Z40 



ndll. of fig. 2 



