Mr Wilson, On a Sensitive Oold-Leaf Electrometer. 135 



On a Sensitive Gold-Leaf Electrometer. By C. T. R. Wilson, 

 M.A., F.R.S., Sidney Sussex College. 



[Read 2 March 1903.] 



The electrometer has the form shown in the accompanying 

 figure. (Fig. 1.) 



Fig. 1. 



The case consists of a brass box with flat sides, of dimensions 

 4 cms. x 4 cms. x 3 cms. 



The gold-leaf is a narrow one, less than 2 mm. wide and about 

 3 cms. long, with straight, clean-cut edges. It is attached to the 

 end of a brass wire which passes through a sulphur plug in the 

 centre of one of the narrower walls of the vessel. Opposite it, and 

 supported on a brass rod passing through a similar sulphur plug, 

 is a rectangular brass plate nearly equal in size to the inner 

 surface of the wall, from which it is distant about 1 mm. 



Small glass windows in the square sides of the case allow the 

 position of the gold-leaf to be read with a microscope provided 

 with a micrometer scale. The magnifying power was such that 

 54 micrometer divisions corresponded to a movement of 1 mm. 



