Lord Kelvin. On a new Form of Air Leyden, [June 2, 



IV. " On a new Form of Air Ley den, with Application to the 

 Measurement of Small Electrostatic. Capacities." By LORD 

 KELVIN, P.R.S. Received May 31, 1892. 



In the title of this paper as originally offered for communication 

 " Air Condenser " stood in place of "Air Leyden," but it was accom- 

 panied by a request to the Secretaries to help me to a better designa- 

 tion than "Air Condenser" (with its ambiguous suggestion of an 

 apparatus for condensing air), and I was happily answered by Lord 

 Rayleigh with a proposal to use the word " leyden " to denote a 

 generalised Leyden jar, which I have gladly adopted. 



The apparatus to be described affords, in conjunction with a suit- 

 able electrometer, a convenient means of quickly measuring small 

 electrostatic capacities, such as those of short lengths of cable. 



The instrument is formed by two mutually insulated metallic 

 pieces, which we shall call A and B, constituting the two systems of 

 an air condenser, or, as we shall now call it, an air leyden. The 

 systems are composed of pa.rallel plates, each set bound together by 

 four long metal bolts. The two extreme plates of set A are circles 

 of much thicker metal than the rest, which are all squares of thin 



FIG. 1. 



