1881.' 



on the Phenomena of the Electric Discharge. 



471 



twenty-five times; TiOO eells have, as you sec, a very short striking 

 distauec ; it is only 0*00008 inch, so that tlie S2)ark obtained with the 

 cascade is IGl times as h)ng as with the battery alone. If there were 

 no loss in converting (|nantity into potential, it would be G25 times 

 or the square of 25. The apparatus I am using is the so-called 

 Rheostat of Gaston-Plante. Franklin, it will be remembered, was 

 the inventor of the cascade. It is not impossible that the eftects of 

 lightning may at times be increased by a kind of cascade arrange- 

 ment formed by the charged layers of cloud floating one over the 

 other. 



Between discs the law of the electric discharge is not the same as 

 between points; its length does not increase nearly so rapidly, as 



Fig. 8. 





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will be seen by a reference to the diagram (Fig. 7), which represents 

 the discharge between two points, a point and disc, between spherical 

 surfaces, and between concentric cylinders. But the increment of 

 potential necessary to produce a discharge for a given distance between 



