and from various effervefcences, as thofe which produce in- 
flammable air, fixed air, and nitrous air. 
29. 1 {hail flnilh the firfl: part of this paper with obferving, that' 
h elides the abovementioued ules, to which our conderfling ap- 
paratus may be applied, the various experiments which may be 
made with it throw great light upon the theory of eleCtric 
atmofpheres in general, of which we arc going to treat m tut- 
fcconcl part. 
P A R T II. 
30. The experiments related in the foregoing pages have 
(hewn how eafily a metal plate, or other conducing plain 
furface, when properly fituated, can draw the cleCtric fluid 
upon itfelf from a weak atmofpherical eleCtricity, from a Ley- 
den phial, &c. lb as to render its effects much more confpi- 
cuous and vigorous. It is now neceffary to give an explanation 
of thole phenomena, the theory of which will greatly facili- 
tate the practical performance of this lort of experiments. 
31. The whole matter, therefore, may be reduced to this, 
viz. that the metal plate has a much greater capacity for hold- 
ing electricity in one cafe, viz. when it lies upon a proper 
plane (as mentioned in § 1 1. 12. 22.) than when it {lands quite 
infulated, as when it is lufpended in the air by its lilk firings 
or infulating handle, or when it {lands upon an infulating 
{hand, as a thick ffratum of reiin or the like. 
32. It is ealy to comprehend, that wherever the capacity of 
holding electricity is greater, there the intenlity of electricity 
Vol. LX XII. U i«- 
