152 



PROCEEDINGS OP THE AMERICAN ACADEMY 



(1.) Charge of the condenser for a short measurable interval 

 followed by discharge through the galvanometer, the discharge 

 occurring about 0.6 sec. after the commencement of the charge, 

 and the contact between condenser and galvanometer lasting about 

 1.2 sec. 



(2.) Charge of the condenser through the galvanometer for a 

 short measurable interval; discharge (not measured) about 1.8 sec. 

 after commencement of charge, the condenser remaining short-circuited 

 1.2 sec. This is the arrangement shown in Fig. 1. 



(3.) Current flowing directly through the galvanometer for a 

 short measurable interval of time. 



C C 



f/'/'A 



B 



a c 



^ 



.^ 





H o 



n. 



Fig. 2. 



C C 



} / y^' 



SP. 



H o 



ni. 



The switch H is always turned to the left except when the arc of 

 contact is to be measured as before described. 



For all the observations on condensers referred to in this paper, 

 the first figure is applicable ; the action is then as follows. 



When the pendulum rests in the latch, one terminal of the con- 

 denser, C, attached to the binding screw 3, is in connection, through 

 the rocking key, with the mercury cup, q, and therefore with one pole 

 of the battery, B, at 4. When the pendulum is released, contact 

 is made between the disks during a certain arc of swing, and the 

 current then flows from the binding screw 5, through the disks and 

 switch H, to the other terminal of the condenser at 2. 



On the pendulum's arriving at the end of its swing, the key is 

 shifted from contact with 4 to contact with 1, causing the condenser 

 to be discharged through the galvanometer ; returning, the pendulum 

 returns the rocking key to its initial position, ready for the next 

 observation. It may be noted that the battery is permanently con- 

 nected with one pole of the condenser except during the return swing 



