﻿of Electricity on Iron Wires. 



431 



regularity was much needed. With the assistance of the 

 mechanician of the laboratory I devised an interruptor which 

 gave very satisfactory results. 



A small electric motor M (fig. 4) was used to produce the 

 necessary motion. This was actuated by the current from two 

 storage-cells, and ran at a fairly constant speed. The armature 

 of the motor was in three sections, and was free from dead 

 points, giving it the great advantage for the present purpose 

 that it could be set in action simply by closing the circuit, 

 making it possible to control it from the observer's station. 



Fig. 4. | Scale. 



The motor was geared to the two-crank shaft K by means of 

 a wheel and pinion. The speed of the shaft K was about 750 

 revolutions per minute, so that about 25 breaks were made 

 per second. The plunging-rods were thinned at so that 



