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Mr. A. L. Fletcher on the 



just possible that the conditions obtained in individual 

 experiments were not always identical with all types of 

 rocks, and that for the more basic carbonates examined a 

 slightly higher constant should be used than that obtained 

 as the mean result of many experiments varying but slightly 

 from the average value 0*6. Should this be so, it would 

 bring the general mean of nearly all the different rock-types 

 examined into striking equality, in view of the fact that the 

 uranium contained by them owes its inclusion to the widely 

 differing causes which the varying nature of their origin 

 involves. 



Constants of tlie Electroscopes. 



About twelve experiments in all were made proper to the 

 constants of the two electroscopes used throughout. From 

 the mean of these below, which were the most reliable and 

 closely agreeing of the standardization experiments, the 

 constants were chosen. 



Experiments on the Constant of the first Electroscope. 



Change. 



Constant. 



Granite, with *003 mo- Uraninite 



0-62 

 0-57 



0-69 

 Mean 0-66 



„ -006 „ 



Granite with a granite-melt containing ] 

 Uraninite 



mg. 





Experiments on the Constant of the second Electroscope. 



Charge. 



1 

 Constant. 



Granite with - 007 mg. Uraninite 



032 



0-73 

 Mean 053 



Granite with a granite-melt containing the Radium 

 in 10 c.e. of a Standard Solution (Rutherford)... 



The following experiments of a comparative nature were 

 made upon the constants. 



