82 Mr. J. J. Watersjton oji some Electrical 



may be presented quite unalloyed with matter in any degree 

 open to question or difference of opinion. 



Experiments on certain forms of discharge. 



1. A disk of sealing-wax, 4 inches in diameter and Jth of an 

 inch thick, held close to the negative excited end of a shell- 

 lac cylinder, then removed and applied to the electroscope, 

 showed no charge; but if before removing it we touch every 

 part of the outer surface of the disk, we find on applying it 

 to the electroscope, that it has acquired a strong positive 

 charge. If we touch only one point, the charge is confined to 

 that point. If we touch with the blunt end of a needle there is 

 no charge; if with the sharp end it is sensible ; if with a brass 

 wire it is sensible ; with a lead point it is still more sensible, 

 even when that point is held an inch or two from the outer sur- 

 face of the disk ; also with gold-leaf. These phenomena vary 

 with the strength of the excitement of the shell lac, also of the 

 material of which the conductor is composed. This last fact is 

 distinctly impressed on the mind after frequent repetition of the 

 experiments. 



2. To examine this further, I worked with a jar having about 

 two square feet of coated surface. Its uncoated part was covered 

 with shell lac applied when the glass was hot, and the edges of 

 the tinfoil were covered with sealing-wax, as also the lower part 

 of the jar outside, where the curve was sharp. On the top of the 

 jar was a cake of lac, with a sealing-wax handle to take it off and 

 on ; and through its centre passed the charging-rod, which was 

 coated with soft wax, as was also the knob, which was a brass ball 

 2 inches in diameter. The jar rested on a cake of sulphur which 

 rested on an insulating stool, and was charged by means of an- 

 other rod and ball uncoated, which was removed after the charge. 

 The soft wax that covered the ball was composed of a mixture of 

 beeswax, resin, and red lead. It was heated and rendered semi- 

 liquid before placing on the jar; then, before it hardened, the 

 point of an uninsulated needle was presented about an inch from 

 the knob (first having touched the outside of the jar). Instantly 

 the coated semiliquid surface of the knob opposite the needle 

 was pitted with innumerable small holes, occupying an exactly 

 circular space of three-quarters of an inch diameter. By taking 

 away the needle, touching the outside of the jar, then bringing 

 the needle to its former position, the action could be sustained 

 (until the coating became hard), having the appearance of a 

 shower of particles as from a watering-pan. 



The pitted space being then examined by a lens, the appearance 

 was exactly as if a shower of minute projectiles had been forcibly 

 driven through the wax coating to the metallic surface of the 



