Th. 49. N. 13. Tin plates at 17 inches from wire. With electrometer at 1 + 3. It was found on looking at the plate of crown glass that there were narrow fringed rings of dirt all round the edges of the coatings, the space between these rings and the coating being clean. This was supposed to be done by the explosions. The distance of these rings from the edge of the coating seemed nearly the same both within the slits and without, but of the 2 seemed less within the slits. The mean distance seemed about 105 inc. which seems to shew that the electricity spreads pretty nearly the same both within the slits and without. Something of this kind has been frequently observed in the sliding trial plate 1 and sometimes I believe in some of the coated glass plates. Sun. Feb. 14 [1773]. Th. 49. N. 17. Last exper. repeated. [At 1+ 3, Sum = 29.6, at 3+1, Sum = 28.3. Plate D gave 26 and 27.5 respectively. See Art. 664.] 539] Experiment to determine whether the charge of a Leyden vial bears the same proportion to that of another body when elect. is very weak as when it is strong†. AB is a tin cylinder 14 feet 8.7 inches long and 17·1 inches in circumference. DC is a brass wire 371 inches long and 15 in diameter; both supported by non conductors; with the middle sized cork balls hung at D. FE communicates with the prime conductor and is charged till light paper electrometer separates. A brass wire is suspended by silk, so as to be made alternately to touch E and DC. Mon. Feb. 15 [1773]. Th. 55. N. 22. The cylinder AB and wire DC were electrified negatively till the balls separated about 1 diameter. On touching DC twice with the wire, the corks separated about as much positively. The wire was 27.6 inches long and 15 in diameter. * [Art. 308.] + [See Arts. 358, 666, and Note 25.] The cylinder AB was then taken away and the plates D and E placed under the wire DC. The wire was obliged to be changed for one 20-8 inches long to exhibit the same phenomenon. [See Art. 666.] Tu. Feb. 16 [1773]. Th. 57. N. 20. Same exper. repeated. Cylinder touched twice with wire 31 inches long; changed from about 1 diam. neg. to D° pos. D and E with wire 24 inches D°. cyl. with wire 31 Do. cyl. with 27 did not. [See Art. 666.] 540] Lane's electrometer compared with straw and paper electro meters. # [Revolutions and 60th parts of a revolution. One revolution = 038 inch.] 541] Crown and H with slits compared with white cylinder; also on the excitation of electricity by separating a brass plate from a glass one. Wed. Feb. 17 [1773]. Th. 55. N. 21. [6 observations, Art. 660.] Fr. Feb. 19 [1773]. Th. 53. N. 181. A plate of glass 11 inches square, coated with tinfoil 8 inc. in diameter, was supported on waxed glass. A brass plate 8 inc. in diameter was supported over it by silk strings in such manner as to lye on the plate perpendicularly over the tinfoil, and to be drawn up till it touched a piece of wire supported on waxed glass with the middle sized cork balls suspended from it. This was done in order to see how much of the charge of the plate was contained in the coating. It was found that though the plate was not electrified, yet on lifting up the brass plate the balls separated some inches if the tinfoil communicated with the ground, but if it did not communicate, the balls, as well as I remember, separated considerably less. Some bits of thin silk thread were placed between the glass and brass plate. In the afternoon. Th. 54. N. 171. The experiment repeated with bits of card between the glass plate and brass. When tinfoil commun. inch. } {did not commun.) with ground, balls sep. about When there was nothing between the glass and brass plate, they sep. 1.4 inc. whether the tinfoil communicated with the ground or not. In all these cases the brass plate was negative. The glass plate was found to be pos. if the tinfoil did not communicate with the ground, but I could not perceive it to be at all electrified if it did communicate. The next morning the experiment was repeated, but the balls separated much less than before. The temper. of the air was much the same. 542] It was tried whether when three tin plates 1 foot square were placed near to and parallel to each other, the line joining their centers being perpendicular to their planes, the middle plate would receive much electricity on electrifying the plates*. The experiment was tried with the same apparatus and nearly in the same manner as the experiment with the globe †, except that the two outer plates were suspended by two sticks of waxed glass turning on hinges. The wire too by which the plates were electrified was made so as to touch all three plates at the same time. Four bits of sealing * [Exp. VIII., Art. 288 and Note 23.] + [Art. 218.] wax were stuck to the middle plate, two on each side, to prevent the outer plates coming too near. Sun. Feb. 21. Th. supposed about 55. N. 201 If the bits of sealing wax were of such size that the distances of the (1.15 outer plates were about the middle-sized cork balls separated (1·65 ' about 5 The light paper electrometer was used in this experiment. If the globe 2 was electrified in the same degree, and its electricity communi(the 4 jars cated to and the middle tin plate electrified by one of 1, 2 & 4 jars these jars (the two outer being drawn aside) and the cork balls then drawn up against the plate, they separated about 5 case the electricity of the globe was diminished and therefore when the outside plates were at tricity in the middle plate was about [times], of what it would have received by the same degree of electrification if placed by itself. 543] Charge of A, B, and C laid on each other without any coatings between; also charge of 1st thermometer tube. The coatings were taken from the 3 plates A, B and C of Nairne, and the plates cleaned and placed one on the other without anything between them, and stuck together by dropping some melted wax on the edges. The outside surfaces were then coated with circles 6.6 inc. diam. This is called Triple Plate*. A thermometer tube was coated with coatings 11 inch long, the inside being filled with ☀, with wire let into one end, and the ends stopped with cement. The tube was 12.7 inc. long; weighed 1..3.. 0, and the bore held 22 gra. of water, the specific gravity of a piece of the same tube weighed twice over was 11.7 = 3.1. 3.1531 N.B. The comp. pow. of this tube is about 90. This is called Tube 1†. Mon. Feb. 22 [1773]. Th. 53. N. 201. [8 observations. Art. 675.] 544] Lane's electrometer compared with straw and paper electrometer; also charge of plate rosin with brass coating made to prevent spreading of electricity. A plate of rosin and bees wax of the same proportions as for exper. rosin was cast of the shape of figure, ABDC and abcd being brass plates 2.45 in. diam. their distance before the rosin was poured in being about 12 inc. Tu. Feb. 23 [1773] in afternoon, the rosin plate being cast that morning, the hygrom. as well as I remember being about 22. [4 observations, comparison with E.] Wed. Feb. 24 [1773]. Th. 54. N. 20. [4 observations.] Rosin closed in about 7", sep. again in 35. E was irregular. 545] Second thermometer tube; also comparison of charge of cylinder used in [Art. 539] with D + E. 21 A thermometer tube whose length was 22.1 inc., weight = 2, 17, and weight water which filled bore 14 gra. was coated with tinfoil 15.5 long, conseq. comp. power * the spec. gra. of a part of the same tube being 3.243. = Fr. Feb. 26 [1773]. Th. 52. N. 201. The cyl. used in [Art. 539] compared with the plates D and E, the wire Mm of machine being drawn out to 39 inches, and resting on the cylinder as in that experiment. A sliding trial plate on neg. side. [6 observations. See Art. 666.] 546] Charge of second thermometer tube; also that of rosin plate with brass coating; also that of A, B, and C laid on each other without coatings between. [10 observations. Art. 675.] The same things were tried the day before, Th. 55, N. 171, but the wire for making communication between machine and ground was forgot to be fixed. [14 observations. See Art. 666.] 547] The quantity of electricity in Plate D compared with that in a tin circle of 36 and another of 30 inches diameter by means of |