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ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 3 



by far the most successful of these devices is the well-known Wims- 

 hurst machine, which was first invented in about 1878. This ma- 

 chine is well known to everybody, I think, as the " influence ma- 

 chine ", whose action may be described as follows : 



Imagine that, in some way or other — for example, by friction — a 

 small negative charge is located on the metal sector of the rotating 

 disk opposite the point G of figure 2. This negative charge will 



FiGDRD 2. — Schematic diagram of Wimshurst influence machine. 



induce the separation of positive and negative electricity in the metal 

 rod CD^ drawing positive charge to the point G and forcing negative 

 charge to the point D. At these two points the charges are collected 

 on the metal sectors of the second glass disk which is rotating in the 

 opposite direction. Thus all the metal sectors to the right of G carry 

 positive charge collected from G and they all deliver it to the sharp 

 peedle point at F, 



