160 



PROCEEDINGS OF THE AMERICAN ACADEMY 



Fig. G. 



Time of charge, 0.93 sec. Unit of abcissas, 1 mf. Unit of ordinates, 10 ma 



Fig. 7. 



Time of charge, 2 sec. Unit of abscissas, 1 mf. Unit of ordinates, 10 mc. 



It will be noticed that all the curves in all those squares which 

 have any one number in their upper left-hand corners, have the same 

 slope at the origin. This slope is numerically equal to one tenth* of 

 the electromotive force in volts of the charging batteries, as computed 

 from measurements of such cells in open circuit made with a Quadrant 

 Electrometer. 



* Each vertical unit corresponds to ten microcoulombs. ' 



