449] From these experiments the quantity of electricity in 221 450] Experiments to determine whether the quant. el. in the large circle was the same whether it was supported on waxed glass* or on silk strings, the trial plates, which were of wood covered with tinfoil being supported on waxed glass, the large trial plate drawn out to n inches being expressed by Ln, the small ditto by S-n. Large circle supported on silk strings. L-5 sep. pos. very sensibly if I staid some time before letting down the wires, but scarce sensibly if I did not. L - 4 seemed to separate, but rather doubtful if I staid, but not if I did not. S5 sep. neg. if I did not stay, but not if I did. L-5 tried again, sep. very little whether I staid or not. The circle supported on waxed glass. L-5 sep. very little whether I staid or not. From these experiments there seems no reason to think that there is any sensible difference in the quantity of electricity whether the circle is supported on silk or on waxed glass. I believe the air was moderately but not very dry when these experiments were tried. The next experiment was made the same night. 451] Experiment to determine whether quantity of electricity in coated glass bears the same proportion to that in a non-electric body whether electrification is strong or weak †. Two pair of corks were made; each separated with rather a less degree of electrification than those used in former experiments. Some lead was then added to those of one pair, so as to double their weight and consequently to make them require 2ce the force to make them. separate. The plate of glass used was the double plate called A in the following experiments, but with coating 1.78 inches diameter. If these experiments could be depended on as perfectly exact the coated plate should contain th part more electricity in proportion when electrified with heavy corks than with light, but this difference is much too small to be depended on. 452] Comparison of two tin circles* 9.3 inches diameter with one of 18.5, the tin plates supported on waxed glass and touched in the same manner as wires, the trial plates supported on silk strings. Small plates at 36 inches distance tried again. sep. very little with L 1, which is the same as before. 453] A brass wiret, 72 inches long and 19 thick was then tried, touched by middle of touching wire. L-2 sep. pos. S2 very little neg. 15.57 * [Art. 273 and notes 11 and 21.] + [Art. 279.] 455] TRIALS OF CHARGES. 223 454] From these experiments it should seem as if el[ectricity] in Large circle touched at extremity at middle -14.63 13.55 were Two small circles at 36 inches 13.15 If the two circles were placed at the same distance from each other in the same manner as in coated plates, and were electrified by wires touching their centers perpendicularly, the quantity of electricity should be The quantity of] el[ectricity] in the wire 72 inches long and 19 thick seems to be nearly equal to that in the circle of 18.5 inches. Therefore if we suppose quantity of electricity in a cylinder to be proportional to its length divided by the logarithm length of thickness that in globe 4761 to tab. log. -or as 1096 to N log. whose diame thickness cylinder as and the quantity of electricity therein is to that in a circle of the same diameter as 455] A trial plate for Leyden vials consisting of two plates with rosin between. 456] Therefore the quant. el. in these bodies seems as follows: = Diameter of the globe 121, therefore quantity of electricity in globe is to Do in circle of same diameter as 1.56 to 1*. 457] Two trial plates were made on a piece of the large bit of ground glass, one 2.37 inches diameter on place where the thickness = 1.80, computed power 312; the other 2:57 inches diameter where thickness = 1.90, computed power = 34.8. = The first is called S the other L. +The plates of ground glass E and F were each coated on one side with a circle 7.95 inches diameter communicating with coating on the other side. These plates were kept from touching by three bits of sealing-wax. When the coatings were kept at distance 39 from each other this is called plate of air 39 thick, &c. A piece of wire of the same thickness as the other was made to slide thereon. When the plate of air was tried against trial-plate S with wire drawn out 12 inches it is expressed 458] The wire not drawn out is about 40 inches, and may therefore contain about 10 cyl.* inc. of electricity, id est, as much electricity as is contained in circle of 10 inches diameter. Quantity of electricity in additional wire is supposed to be equal to its length [divided] by 4.4. Both the trial plates together, whose computed power 66, is equivalent to 2A+ 2B + 80 inches of wire + 45 of additional wire, id est, to 73·4 +20 + 10·1 = 103.5 inches of electricity, therefore 1 inch of computed power in the glass of which trial plates are made should be equivalent to 141 inches of electricity. By the experiment marked in [457], a difference of computed power in the trial plates = 3.6, which is equivalent to 5.08 inches of electricity, was equivalent to drawing out wire 20 inches, which is supposed = 4.54 inches of air, which is as near an agreement as can be expected. By a medium of the experiments, the plate of air 39 thick required wire to be drawn out 11 inches less than A and B, the different experiments varying from 9 to 14, therefore the plate of air contains 2.6 inches more electricity than A and B, id est, it contains 39.3 inches of electricity. The plate of air 343 seemed by 1 experiment to contain 42.7 of electricity. Therefore plate of air 39 contains 4.94 times more electricity than a circle of same diameter, therefore quantity of electricity therein is to that in circle of same diameter as radius to thickness × 2.06 or quantity of electricity = computed power × 243. 459] Four irregular pieces of glass, N, O, P, Q, were coated with circles. The thickness, specific gravity of glass and diameter of circles are marked in [Art. 370], the thickness of glass being found by taking thickness with calipers at center of proposed circle, and finding a part of outside of same thickness and measuring that part by Bird's instrumentt; the computed power of all being just 40. The experiments were tried with sliding wire as former[ly]. |