2 66 Mr . Nicholson’s Experiments and 
apparatus. A denfe ft ream of electricity appeared between the 
rod and the filk, and the conductor gave very many fparks. 
5. The knob of a jar being fubftituted in the place of the 
metallic rod, it became charged negatively. 
6. The filk alone, with a piece of tin-foil applied behind it, 
afforded much eieCtncity, though lefs than when the cufhion 
was applied with a light preflure. The hand, being applied to the 
filk as a cufhion, produced a degree of excitation feldom equalled 
by any other cufhion. 
7. The edge of the hand anfwered as well as the palm. 
8. When the excitation by a cufhion was weak, a line of 
light appeared at the anterior part of the cufhion, and the filk 
was ftrongly diipofed to receive eleCtricity from any uninfulated 
conductor. Thefe appearances did not obtain when the exci- 
tation was by any means made very ftrong. 
9. A thick filk, or two or more folds of filk, excited worfe 
than a fingle very thin flap. I ufe the filk which the milleners 
call Perfian. 
10. When the filk was feparated from the cylinder, fparks 
paffed between them ; the filk was found to be in a weak 
negative, and the cylinder in a pofitive ftate. 
The foregoing experiments fhewthat the office of the filk is not 
merely to prevent the return of eleCtricity from the cylinder to 
the cufhion, but that it is the chief agent in the excitation ; while 
the cufhion ferves only to fupply the eleCtricity, and perhaps 
increafe the preffure at the entering part. There likewife feems 
to be little reafon to doubt but that the difpofition of the eleCtri- 
city to efcape from the furface of the cylinder is not prevented 
by the interpofition of the filk, but by a compenfation after the 
manner of a charge ; the filk being then as ftrongly negative as 
the cylinder is pofitive : and, laftly, that the line of light 
between 
