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Mr. TV. Morris Jones : Frlctional 



small T-shaped strips of ebonite, which could be firmly fixed 

 to an ebonite holder, fig. 1. The holder was made of two 

 pieces of ebonite connected across by a block of well insu- 

 lating amber, and could be fitted into a bayonet-socket 



forming one arm of a lever bent at right angles. The lever 

 turned about an axle fixed in the wooden framework sup- 

 porting the wheel, so that, when the holder was in position, 

 this arm of the lever was vertical with the specimen pressing 

 horizontally against the rubber, the thrust between the 

 specimen and the rubber being produced by a lead weight 

 placed in any suitable position on the other lever-arm. A 

 rub was effected by releasing the wheel, which was then set 

 rotating by the falling weight, the specimen being separated 

 from the rubber just before the w T heel came to rest. Know- 

 ing the time of fall of the weight, the kinetic energy lost on 

 impact of the weight with the floor could be taken into 

 account in the calculation giving the work spent against the 

 friction of the specimen on the rubber. The amount of 

 energy lost at the bearings of the wheel was small and could 

 be neglected. 



Immediately after a specimen was rubbed, the holder 

 supporting it was quickly withdrawn from the socket and 



