500 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



TABLE XXXI. (Figure 6.) 

 " Par. AA " vs. Air. 



TABLE XXXII. (Figure 5.) 

 " Mica B " vs. Air. 



In working up the data here printed to derive the results shown 

 in Table XXXIII, below, the following method was used : 



I first determined from the observations the ratios (R) of the throw 

 obtained to the charging voltage and set the R's opposite the corre- 

 sponding charging intervals. Then I found mean values of the R's for 

 the various charging intervals. Then that R which I believed to cor- 

 respond to the shortest charging interval secured was taken as a 

 standard of comparison and the unknown residual charge in centimeters 

 of throw per volt which had already been formed in the condenser in 

 this shortest obtainable charging interval was called x. By taking 



