234 



insulating support D and sliding in it. From the zinc-plate^ 

 standing on a plate of ebonite, goes a copper wire to the 

 inner coating of a Leyden jar L and continue to one sphere of 

 a spark-micrometer iY, the other sphere of it being connected 

 with the earth e together with the outer coating of the jar. 



Supposing the cap. tube to be absent and the machine 

 put in motion, a series of sparks is going on between the 

 spheres of the micrometer, which shows that the jar is 

 charged and discharged. The electricity, which charges the 

 jar passes from the point s through the air-layer to the 

 water in the vessel and hence to the Leyden jar and the 

 spheres of the micrometer to the earth. 



If the capacity of the Leyden jar is C and the poten- 

 tial on one sphere V (the other 0) the quåntity of electricity 

 which passes in every spark is M. 



ilf=CFE.S.E. 

 and if the number of sparks in a rainute is n, we shall 



have, as G is Far. and F=: 300 Volt 



1 nM 1 



nM=nM^—^ Coul.^-^^^^ amp. 



The intensity of the current through the cap. tube and 

 the glass-vessel can thus be expressed in amp. when C and 

 V are known. We prefer to use the relative measures in 

 the lollowing, but will give the necessary dates to calcu- 

 late them in amp. — The machine in use was the author's 

 modification of the Wimshurst machine i. e. with cylinders, 

 instead of discs, rotating in the opposite directions and was 

 hold in the same strength. When the handle made 60 turns 

 a minute the cyhnders made 87. 



The cap. tube which, in the beginning, had a length 

 of 10,3 cm and a diameter of 0,5 mm, was put in its po- 

 sition (see the fig.). With a hall and tube af india-rubber 

 the water was soaked up and after its falHng down the 

 tube had been moistened. After an interval of 0,5 minute 

 the machine was put in motion and the current began to 



