PIERCE AND EVANS. — CAPACITY OF CARBORUNDUM. 



801 



current and number of charges or discharges per second, we have taken 

 to indicate that the charge and discharge were practically complete at 

 each commutation ; for it is apparent that if this charge or discharge 

 were not complete the incompleteness would be greater at the higher 

 frequencies of commutation and we should not have the linear relation. 



10 20 30 40 eo 



Figure 7. B positive. Charge current vs. no. charges per second. 



10 20 30 40 eo 



Figure 8. B positive. Discharge current vs. no. discharges per second. 



There follows a mathematical investigation of the phenomenon with 

 the assumption of a complete charge and discharge at each cycle of the 

 commutator. The problem is an interesting one on account of the fact 

 that the leak current through the crystal is not proportional to the 

 voltage. 



VOL. XLVII. — 51 



