472] Comparison of two tin circles 9.3 inches in diameter with one of 18.5; the two circles being placed in vertical planes parallel to each other and perpendicular to the vertical plane joining their centers and the trial plate, their centers being both in the above-mentioned plane*. There was a distinct touching wire to each plate meeting each other at R, the two wires were kept asunder by a slender glass tube, and about 1 inch of the end of the wires bent at right angles horizontally in order to touch the plates by being let fall on their edges. When the large circle was tried, this double touching wire was removed and a single one used in its room, which was sometimes fastened to the middle of the glass tube, and sometimes used without it, as will be expressed. The height of the top of the circles above floor = 4'. 3". The center of the large circle when that was used, or the middle point between the centers of the two small circles when they were used, was (8'. 10") from (vial 17. 3") {middle of trial plate}. The circles were suspended by silk strings. touching wires for the circles was 36 inches. The length of the 473] Monday Dec. 30 [1771]. Th. 50o. S. H. 18. Two small circles at 18 inches from each other. Large circle, touching wire being fastened to glass tube. The Proportion by theory, vide P. 14 of calculations*, are as fol 474] The same experiments repeated in the same manner except that the distance of the center of the large circle, or of the middle point between the centers of the small ones was 5'. 3" from the vial, and the middle point of the trial plate 8'. 2" from vial, and that some boards forming a floor about 4 or 5 feet square was placed under the circles 14 inches from the ground, and that a perpendicular bar of the same breadth as those of the frame was placed 5 inches nearer to the circles than the other, so that the distance of the center of the large circle from the vial and the ground, and also the distance of the nearest small *["P. 14 of Calculations" refers to a rough calculation in parcel No. 6, which is an early form of Props. XXIX. and XXX. See Arts. 140-143. "P. 14" contains the following remark, which fixes its date after Art. 456, "By exp. P. 15 [Art. 456] quant. el. in circle is to that in globe of same diam. as 1 : 1·56 :: : 78, 2+n therefore =78." Here n is the reciprocal of p in Art. 140.] 2+2n = + [See Art. 681 and Notes 11 and 21.] circle from the perpendicular bar when they were placed at 36 inches distance, were diminished in about the ratio of 2 to 3*. 475] Tu. Dec. 31 [1771]. Th. 51o. S. H. 18. Small circles at 18 inches distance. 476] Comparison of 2 wires 3 feet long and inch in diameter with 1 of 6 feet long and 185 in diametert. The wires were placed parallel to each other, horizontal and perpendicular to the horizontal bar. They were touched almost close to one extremity by the same wires and in the same manner as the circles in the former experiment. The That end of the wires near the part which was touched was suspended by silk, the other end was supported on waxed glass. distances were the same as in [Art. 472]. 477] Fr. Jan. 3 (1772). Th. 50°. S. H. 191. C. H. + 2. Short wires at 18 inches distance. C-4 sep. B-8 do. Proportion. 1 By theory [Art. 152], the proportions should be between those of 478] Comparison of different substances tried in the usual manner*. The large tin circle suspended by silk. •9323 •9053 ⚫8827 •8926 ⚫8597 ⚫8353 [Article]. [1] [2] * [See Arts. 653, 654, 682.] + Double plate ground glass A, thickness 3, diam. coating 1·82, comp. power 11.04. B, 31 1.855, 11.1. A tin cylinder 35.9 inches long and 2.53 in diameter, on do. A tin cylinder 54.2 long and 73 in diameter, on do. A-191 B-5 17.89 4.07 15.85 [9] Brass wire 72 inches long and 185 in diameter, on do. 479] According to the 5th and 6th article of last page, the quantity of electricity in the square is to that in a circle of the same area as 1.08 to 1, and that in square to that in oblong of the same area as 991 to 1. By comparing the 2nd article with the 3 last, the quantity of elec(thick cylinder tricity in thin cylinder may be to that in a globe whose diameter wire Therefore, if we suppose that the real quantity of electricity in any cylinder is to that in the globe whose diameter equals the length of the cylinder as 1 to N. L. 2e length 2ce length or as 4964 to tab. log thickness' it will agree very well both with theory and experiment. Or by comparing this with the first article, the quantity of electricity in any cylinder is to that in a circle whose diameter is equal to the length of the cylinder as 759 to tab. log 2ce length Comparative charges of bodies tried in the former experiment. By means of this experiment and that of 1771. [A:ts. 455, 456.] If the charge of the globe is called 1, that of the circle will be 992, therefore, by comparing 6th and 7th articles with 5th, the charges of the square and oblong will be 957 and 965. *[Exp. vii. Art. 281.] |