Tried by pith balls hung by threads. A and B are the coated plates A and B, the bottoms of which communicate with the ground, D and d are two bits of wood resting on them, supporting the pith balls E and e. G is a bit of wood for making a communication between them. The wire for electrifying the plates rests on B, and is so contrived that when that is lifted up the wood G is let fall on the plates. The pith balls E had bits of wire made to run into them in order to increase their weight. A paper with divisions was placed 6 inches behind the pith balls and a guide for the eye 30 inches before them. Tu. Oct. 26 [1773]. Th. 60. Com. -63. N. 21§. One of the balls E with its string weighed 5 gr. and its wire 14, the other 6 gr. and its wire 1.7. The two balls and strings together-the weight of one of the strings weighed 105 gr., the weight of the string about '05, the weight of the two wires together was 3.2. When the wires were taken out of the balls E, and a communication made between the two plates, while the electrifying wire rested on B, then when balls e sep. (1.2 balls E sep. (1.25 1.14. 1.08' The wires were put into balls E and the jars electrified while the electrifying wire rested on B. When the balls E sep. 1.3 inc. the electrifying wire was lifted up and the electricity of the plates taken away, immediately after which the electrifying wire was let down and immediately drawn up again when the balls e separated to 1:44. The electrifying wire being then let fall on B and suffered to remain, the balls E separated to 1.14. The jars were charged, and the electricity diminished by alternately drawing up and down the electrifying wire and discharging the electricity of the plates till the balls e separated to 1.2; then letting the electrifying wire rest on B, the balls E separated to 1·08. Wed. morn. The new heavy electrometer made with large wood ball and pith ball separates when the balls E separate to 1.52, and new light electrometer separates when the balls e separate to 1·44. When balls e separate to 1·44, balls E separate to ‘96. The new heavy electrometer above mentioned separates about or inch when old light cylinder electrometer just separates. Result of these experiments. Balls E without weight separate farther than balls e with the same degree of electrification. If balls of given weight separate 15 with given degree of electrification, balls of 4 times weight separate 96, therefore if balls of given size are electrified in given degree, the distance to which they separate Therefore, in last paragraph, if balls of given weight separate 1.9 balls of their weight will separate to 1.22 1.5 1.25' therefore if balls of given weight with given quantity of redundant fluid separate to given 475 distance balls of that weight separate to same distance with half that quantity of redundant fluid. 526] Whether the charge of plate E bears the same proportion to that of another body whether the electrification is strong or weak: tried by machine for Leyden vials. Wed. Oct. 27 [1773]. Th. 61. Com. 8. N. 201 Plate E of Nairne on neg. side against sliding tin plates placed at end of long wire [20 observations]. Result. Therefore with light electrom. the plate E is balanced The plate E is balanced by 37 inc. el. 527] Plain wax and 3rd dephlegmated wax with E + F and 5th rosin with double plate A and B. Also small ground crown with D+ E + F, and large do. with C. The coatings were taken off from 4th rosin, and coatings 1.79 inc. diam. put in their room. This is called 5th rosin. A plate of dephlegmated bees wax was also made [120]* inc. thick and coatings put on 3-525 inc. in diam. This is called 3 dephlegmated bees wax. A plate of plain bees wax was also pressed out [119]* inc. thick and coatings put on 3.475 inc. diam. * [These measures are left blank in the Journal. I have supplied them from Art. 371.] A piece of thick crown glass was procured from Nairne about 26 thick and ground down equally on both sides to about 07 inc. thick. Two circular coatings were put on, one 3·54 inc. in diam, the other 2·035. Wed. Jan. Th. 56. N. 27 [16 observations]. 528] K, L and M compared with D + E + F at distance and close together; also large ground crown with C and small one with D + E + F ; also 3rd dephlegmated wax and plain wax with E+ F; also 5th rosin with double B. Friday, Jan. 29 [1773]. Th. 31. N. 161. Tried with middle sized cork balls and a new white large trial plate [18 observations. Art. 656]. 529] K+L+M compared with A, B, and C; also A + B + C with H. Sat. Jan. 30 [1773]. Th. 50. N. 161. [20 observations. Art. 657.] 530] K+L+M compared with B with electrification of different strengths. Sun. Jan. 31 [1773]. Trial plate F enlarged. [14 observations with light and heavy electrometer alternately. Art. 656, 658.] 531] K+L+M with A, B, and C; also D + E + F with K, L, and M; also small ground crown with K, L, and M; and D + E + F and large ground crown with A, B and C and K+L+ M. Mon. Feb. 1 [1773]. Th. 48. N. 16. [20 observations. Art. 657.] 532] On light visible round edges of coated plates on charging them*. Mon. Feb. 1 [1773]. Th. 48. N. 16. Some coated glass plates were placed on pos. side and electrified in usual manner in dark room in order to see whether any light was visible round their edges. With the plates M and L of Nairne and with the small ground crown glass a light was visible round the edges when the light electrometer was used, and nearly equally so with the large ground crown glass. The light seemed of the 2 rather stronger with the plate F and A of Nairne; no light was visible when light electrometer was used, but it was with the heavy electrometer. 533] Crown A and C and large ground crown with C; also 3rd dephlegmated wax, plain wax and sliding plate 3 with E+ F; also 2 double plates with E, F, and D. * [Art. 307.] Mon, evening. Th. 53. N. 15. [25 observations. Art. 655.] 534] Charge of the triple plate-the three plates A, B and C placed over each other, with bits of lead between coatings*. The three plates A, B and C were placed over one another with the coatings nearly perpendicularly over each other, with bits of lead between them, so as to keep them at the distance of † inches from each other. This compound plate was tried in the usual manner. Tu. Feb. 2 [1773]. Th. 50. N. 171. [9 observations. Art. 677.] 535] Whether the charge of plate D bears the same proportion to that of another body whether the charge is strong or weak: tried with machine for Leyden vials. [Art. 664.] Th. Feb. 4 [1773]. Th. 481. N. 131. Tried with smallest cork balls and the light straw balls as electrometers. The plate D placed on the neg. side and the sliding tin plates at 231 inc. dist. from wire. 536] H with slits and a crown glass with oblong coating compared with white cylinder; also A and C with slits compared with B. The coatings were taken off from the plates A, C and H, and oblong coatings with slits put in their room; an oblong coating without slits was also put to a piece of crown glass, vide Measures [Art. 593]. Tu. Feb. 9 [1773]. Th. 50. N. 12. 50 observations. 50 observations. Art. 660. These plates were tried with middle cork balls. Spreading of el. on surf. A & C. Balls at first sep. wider. Closed in about 10". B. D°, but rather sooner. As it was supposed that this proceeded from the wires not conducting ready enough, the machine was moved slower, there was then but little of this and B was a great while before it closed, C about 5", H a great while. It was suspected that this increase of separation of the balls before they closed was owing to the wire designed to carry off el. to earth* not conducting fast enough. To try this, the next evening a long wire was insulated, and the cork balls hung to it. It was electrified sufficiently to make them sep. about an inch. They closed instantly on touching the wire with a bit of iron either communicating with wire for carrying off el. to ground, or whether it was only held in the hand. The air was as dry as the night before. 537] Crown with slits and H with Do compared with white cylinder; and A and C with oblongs compared with B†. The coatings were taken off from the plates A and C and oblong coatings without slits put in their room. The coatings were also taken from the crown glass, and oblong coatings with slits like those put to C put in their room. Fr. Feb. 12 [1773]. Th. 49. N. [34 observations, Art. 660.] 538] Experiment of p. 61 [Art. 535] tried with small ball blown to the end of a thermometer tube. A ball rather less than inch diam. was blown at end of glass tube and was coated on outside with tinfoil, the inside being filled with. This was used instead of plate D in exper. to see whether charge of Leyden vial bore the same proportion to that of another body whatever force it was electrified with. It was found that 12 inches of this tube when coated contained as much el. as K + 8 D, and therefore the spreading of the el. inch on surface of this tube increases its charge by D, whereas the spreading of el. on surface of D increases its 18 charge by 1 51 D. 30 |