I 5 2 Experiments on Coated Plates 



To these two bars are fastened four upright sticks of glass covered 

 with sealing wax; they are represented in the figure and shaded black, 

 but are not distinguished by letters to avoid confusion. To these sticks 

 of glass are fastened four horizontal pieces of wire A a, Bb, Dd, and Ee, 

 and to Bb is fastened another wire mM supported at the further end by 

 a stick of waxed glass. 



Rr is a wooden bar reaching from the wire Ee to the pillar LI, and along 

 the upper edge of this bar runs a wire, one end of which is wound round the 

 wire Ee and the other reaches to the ground and serves to make a communi- 

 cation between Ee and the ground. Cc and Kk are two wires fastened firmly 

 together at k serving to electrify the plate. They are moveable upon K as 

 a center where they communicate with the inside coating of one or more 

 large glass jars, and the same electrometer that was used in the former 

 experiments is fastened to the prime conductor by which the jars are elec- 

 trified, in order that they may be charged to the same degree each time. 



To the ends C and c of the wire Cc is fastened a silk string, as repre- 

 sented in the figure, passing over the pulley S, with a counterpoise w at 

 the other end which serves to lift Cc from off the wires Aa and Bb, or to 

 let it down upon them at pleasure. Gg is a wire the end G of which is bent 

 into a ring, through which passes the wire Ee, so that Gg turns upon Ee 

 as a center. Ff is a wire turning in the same manner on Dd. The ends 

 g and /of these wires are fastened by silk strings to C and c as represented 

 in the figure, in such manner that when Cc rests on the wires A a and Bb, 

 Gg and Ff rest on Dd and Ee, but on lifting up Cc, Gg and Ff are also 

 lifted off from Dd and Ee. 



The counterpoise w is so heavy as to overcome the weight of Cc, and 

 to lift it up till the wires Gg and F/bear against A a and Bb, which prevents 

 Cc from rising any higher. 



Fig. 20 a. 



[Note. This Figure was found among the MS. It is not numbered, nor does 

 any part of the MS. seem to refer to it, but it is inserted here to shew some of the 

 details of a piece of apparatus similar to that described in the text.] 



