518 PROCEEDINGS OF THE AMERICAN ACADEMY. 



charging time increments, thus getting several quotients. Straight 

 lines are now drawn parallel to the axis of charging times, of length 

 equal to the various charging increments and at distances from the 

 axis which are proportional to the quotients obtained for the corre- 

 sponding time-increments, and finally the ends of these straight lines 

 are joined by lines parallel to the ordinate axis. No line is drawn 

 above the time-interval 0-0.00007 second, since the amount of residual 

 charge formed in this interval is unknown, being represented by y per 

 cent of the " free charge." 



After having thus constructed a broken curve for a certain test con- 

 denser, we see that the area under each horizontal part of the broken 

 curve represents the residual charge which was formed in the time 

 interval corresponding to this part. Furthermore, the distance of any 

 horizontal line from the time-axis, or the ordinate of this line, will 

 represent the strength of the average residual forming current which 

 flowed into the condenser during the corresponding time interval. If 

 we had accurately determined the residual charges formed for a very 

 large number of charging times, spaced closely together on the time- 

 axis, the broken curve, constructed as just described, would give an ex- 

 tremely close approximation to the actual residual forming current. 

 As we have data for only three or four charging increments, our broken 

 curves are necessarily very rough ; nevertheless, they give us a correct 

 idea of the general behavior of the current and its high value near the 

 instant of beginning a charge. 



The curves of residual current (Figures 2, 5-11) have been con- 

 structed as just described. In Figure 2 curves are given of both 

 residual charge and residual forming current. A centimeter of ab- 

 scissa represents 0.01 second of charging. 3 A centimeter of ordinate 

 means for the charge curve a residual charge of 1 per cent of the " free 

 charge " of the condenser, and for the current curve a residual forming 

 current which in one second would charge the condenser with a residual 

 charge equal to its "free charge." Accordingly a square centimeter 

 of area under the broken curve is equivalent to 1 per cent of " free 

 charge." All the other figures which show these broken line residual 

 forming currents are on the scale of 1 cm. abscissa for 0.0001 second 

 of charging and 1 cm. ordinate for a residual forming current which 

 would give a residual charge of ten times the "free charge," if it 

 continued to flow uniformly for 1 second after the charging begins. 

 Thus, a square centimeter of area under these curves represents one 

 tenth of one per cent of the " free charge " of the condenser. 



3 Those dimensions have been changed in reproduction, but the square 

 corresponding to 1 or 0.1 per cent of free charge is given with each figure. 



