300 



Prof. R. B. Clifton on the 



[June 14 j 



rod A, projecting from a glass cup B, to the bottom of which it is fused, 

 so that the whole forms one piece of glass. Into the cup B a small 



Fig. 1. 



quantity of strong sulphuric acid (C) is introduced, which appears effectu- 

 ally to dry the inside of the cup and a portion of the glass rod. In many 

 cases, during the time required for an observation, I failed to detect any 

 loss of charge, although six of these supports are used in the apparatus. 

 Even without sulphuric acid in the cup, this form of stand seems to in- 

 sulate fairly well ; for, even in very damp weather, the loss from six such 

 stands rarely exceeded one per cent, of the charge in a minute. 



The electrometer employed was Sir W. Thomson's quadrant electro- 

 meter, in the simple form constructed by the late Mr. Becker, which 

 seems to me to be more sensitive than the more complex instrument, and 

 to give equally reliable results, when it is required only to compare 

 differences of potential. "With this instrument and a condenser one 

 thousandth part of the difference of potential produced by the contact of 

 zinc and copper is very distinctly perceptible. 



The condenser was furnished with horizontal plates, which could be 

 separately levelled, and the upper plate could be moved normally to its sur- 

 face, and adjusted with any required interval between the plates. In 

 observations of the difference of potential between a metal and a liquid, 

 the latter was contained in a glass vessel placed upon the lower plate, 

 and connected with this plate by a strip or wire of the same metal as 

 that covering the lower face of the upper plate. 



A form of key was used by which the condenser-plates can be con- 

 nected by a metallic circuit, while the four quadrants of the electrometer 

 are maintained at the same potential, and the plates of the condenser can 



