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PROCEEDINGS OF THE AMERICAN ACADEMY. 



stances higher below forming voltage than at this point. It may in 

 fact be either lower or higher than the capacity at forming voltage. It 

 will be seen from Figure 17 that if one is working with long charge, 

 short insulation time, and long discharge, the capacity is represented by 

 the curve marked A. Under these conditions the apparent capacity of 

 the plate is greater at low voltages and less at intermediate voltages 

 than it is at the forming voltage itself. This matter will be taken up 

 more fully after the other factors have been discussed. 



3. Short Charge. — Figure 5 shows the arrangement of apparatus for 

 measuring the apparent capacity of an aluminium anode after it has 



been charged for variable 

 short periods of time. The 

 falling weight closes the upper 

 switch, thus completing the 

 circuit from the storage bat- 

 tery through the cell. Falling 

 further, the weight opens this 

 same circuit, and immediately 

 afterwards closes the circuit 

 from the cell through the gal- 

 to cell vanometer. The insulation 

 time, which is determined by 

 the distance between the two 

 lower switches, is kept con- 

 stant at 0.001 second, and the 

 variable charging time is fixed 

 by moving the upper switch 

 up or down on the side rod. 

 Reference to Figure 1 will 

 make this clear. 



The results of measure- 

 ments made in this way show 

 that factors still undetermined 

 play an important role. The previous history of the plate becomes 

 of great importance, and wholly different results are obtained from 

 plates which have been formed slowly and carefully and from those 

 which have been hastily formed, or which have been exposed directly to 

 the voltage of the experiment without previous formation. 



Figure 6 gives a set of characteristic curves of apparent capacity 

 (ordinates) for various short charging times (abscissas). The two 

 curves marked Ai and A 2 are characteristic of a plate which has been 

 very carefully and fully formed. This plate was formed at 340 volts, and 



TO GALVANOMETER 



Arrangement of switches for long charge. 

 Short insulation and varying short discharge 

 times. 



