Two sliding coated plates were made for trying the foregoing, the trial plates being electrified negatively, the others positively. Therefore F seems to contain about as much electricity as C, and D 444] Three coated plates were made on thick plate each 1.8 inches diameter, the mean thickness of glass being supposed 18, therefore the computed power of all three together = 54. All 3 plates together separated pos. With C 465.] 4 5 did not separate. N.B. The breadth of the sliding plate is not known. 445] Small sliding plate not drawn out 14 × 9.4. Large 19 x 13. Globe hung on silk strings negative. Sliding plates on waxed glass positive. [This column gives the side of a square equivalent to the trial plate. See Art. 12.4 did not separate Pasteboard circle 19.4 inches diameter hung on silk strings. With circle 1.8 inches diameter on glass 18 thick it separated a little negatively with plate 19 x 19, and would most likely not separate at 19 x 21 or 19 x 22 20 or 203. Therefore quantity of electricity therein most likely is to that of globe as 20.2 to 124 or as 10: 6. = 446] Thickness of double plate of glass at centre of circle - 285. Diameter of coating = 1.75. Being tried against small plate not drawn out, separated considerably positive, therefore quantity of electricity therein might perhaps be to that in globe as 11 to 18, and therefore its actual power would be to that of thick plate as 6-6 to 18. The computed power is to that of thick plate as 10.8 to 18. A coating 1.45 inches diameter was made on thick plate where the thickness is supposed 168, therefore computed power = 12.5. This being tried against sliding plates was as follows: therefore quantity of electricity therein seems to be to that of globe as 137 to 12.6, or 17·4 to 16·3, id est as 14 to 13, 447] The wires placed horizontally and parallel to each other, one end supported by silk, the other by waxed glass. The trial wire consisted of iron wires 14 thick sliding on each other, supported in [the] same manner. [The charges of the globe and the circle of 19.4 inches appear from these numbers to be as 28.9 30.7. The diameter of the tin circle, 18.5, was probably calculated from these experiments so that its charge might be equal to that of the globe. The correct diameter would have been 19 inches.] Two wires 1 inch thick, 48 inches long, placed 36 inches asunder. Trial wire drawn out 24 inches separated pos. By these it should [seem] as if trial wire required to be drawn out 9 less with the wires at 36 inches distance than with single wire, and 17 less with two wires at 18 inches, whence I should suppose that [the quantity of] el[ectricity] in these three cases was as 96, 87 and 79. The trial wire not drawn out was 70 inches, but the straight part of it was only 51. 448] Wires of half that length tried in the same manner with a shorter trial wire. Two wires 1 thick, 24 long, at 18 inches distance. Trial wire drawn out 1 inch sep. neg. rather doubtful. 3 5 7 did not. Wire 48 inches long, touched by end of touching wire. 449] From these experiments the quantity of electricity in 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 L-n, 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. S 5 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 2 the force to make them separate. The plate of glass used was the double plate called A in the following experiments, but with coating 178 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. 453] A brass wiret, 72 inches long and 19 thick was then tried, touched by middle of touching wire. |