It is plain that the numbers in the 8th or last col. ought to be equal to those in the 6th, as is nearly the case. 664] Whether charge of coated glass bears the same proportion to that of another body whether el. is strong or weak *. pos. P. 61 [Art. 535], E on neg. side tried against sliding tin plates on 60 Charge of E was part less with straw el. at 3+1 than at 1 + 3, the diff. between neg. and pos. el. was much too small to be certain of. P. 66 [Art. 538], a ball blown at end of therm. tube tried in same Charge just the same whether electrom. at 1 + 3 or 3 + 1. manner. P. 68 [Art. 538], charge D° less with el. at 3+1 than at 1 +3. 50 Do 1 P. 82 & 84 [Arts. 551 & 55], tried with machine for finding quant. el. in common plates. No perceptible diff. between charge of E whether tried with el. at 1 + 3 or 3 + 1. 665] By P. 9 [Art. 661], it should seem that el. spread. 034 inc. more on surface with greater degree of el. than with smaller, and therefore as the diam. coating of E or D is 2·16. So that it should seem as if the charge of a coated plate in which the spreading of the el. was prevented would be at least the stronger degree el. than with the weaker. less with 666] By exper. of P. 69 [Art. 539], it appeared that the charge of tin cyl. was to that of D+ E when electrified very weakly as 1.28 to 1, and by P. 70 [Art. 539] as 1-24 to 1. By mean as 1.26 to l†. By mean of P. 76 [Art. 545], the charge of the same cyl. was to that of D + E when electrified in the usual degree as 1.33 to 1. By mean of P. 77 [Art. 546], it came out as 1.37 to 1, but this last can not be depended on, as wire for making communication with ground was forgot to be fixed. * [Arts. 356, 451, 463, 535, 539, 551.] The comp. charge of the cyl. is 484 glob. inc. [See Arts. 358, 539, 545.] The real charge, supposing [See that the wire contains 3.6 glob. inc. less when joined to cyl. than to D+E=73·6, and therefore its real charge exceeds the computed in the ratio of 1.52 to 1. Note 25.] 667] It should seem that the charge of D and E is increased 18 by spreading of el. when elect. in usual degree, therefore if we suppose that the spreading is insensible when electrified in very small degree, the charge of a glass plate is less in proportion to that of another body when electrified with usual degree el. than when elect. with a very small one in ratio of 1.26 to 151, or of 5 to 6. 668] On plate air*. [By Art. 517], P. 32 pl. air 1 cont. 1 inc. el. more than D 33 by mean more than D. The same plate air contained 2 inc. el. less when resting intirely on machine than when resting by 1 corner. [By Art. 517], Pl. air 2 cont. 1 inc. el. less than D + E. By res. P. 5 [Art. 653], D, E, and F cont. 26.3 glob. inc. Therefore pl. air 1 contains 27 glob. inc. 669] [Table of plates of air given in Art. 343.] computed charge above N, the value of N in 3rd col. being 1, in 2nd 1.05, in 3rd 1·1, and in 4th 1.15. The numbers in the 3rd column seem most uniform, and therefore it seems likely that [if] the diam. thickness was very great, real charge comp. charge equal 1.1+. * [See Art. 340.] + [See Art. 347.] would 671] If we suppose the el. to spread 07 inc. on surf. thick plates and '09 on surf, thin ones, the result of Nairne's plates is as follows*. thick white thin white N Р 672] Computations of other flat plates of glass, &c. [Art. 515] P. 28 71.9 [Art. 527] P. 53 small ground crown =D + E + F-4!) - 31 [Art. 531] P. 57 3 * [In Art. 324 the "Real charges " of this table are multiplied by 122 for easy comparison with the computed charges.] The diam. was corrected on supposition that elect. spreads 07 if the thickness of glass = 21, and 09 if thickness=08, and so in proportion in other thicknesses. 674] [Table given in Art. 371.] The correction of the diameter is the same as would be used according to the preceding rule to a glass plate of 2° the thickness, only the correction used is never less than inch. 676] [Table given in Art. 383.] The white jar and cyl. and the 3 green cyl. are corrected for the spreading of the electricity in the same manner as the flat plates, but the 2 therm. tubes are not. 677] On the compound plates*. P. 60, Art. 534. The 3 plates A, B and C placed over each other with bits of lead between contained 8.9 inc. el. less than K or L, therefore its charge =74 inc. The 3rd part of the charge of A, B, or C is 72-6 inc. The coatings taken from the 3 plates A, B, & C, the plates placed close together and the outside surfaces coated with circles 6-6 in diam. 544, P. 75, it contained 7.5 inc. less than D + E + F. 546, P. 77, 6 less. By mean it contains 67 less, therefore charge = 74·5. The thickness of the 3 plates together is 6309. The computed charge of a plate of that thickness with a coating 6.6 in diam. supposing the el. to spread 07 inc. is 9.00, and the real charge of such a plate according to the mean ratio of the real and computed charges of D, E, and F is 74.2. 678] A plate of exper. rosin about 8 inc. square was pressed out, thickness irregular, but at a medium about It was coated with circles 6.61 in diam.† Art. 548, P. 79, its charge = K + D + E 122. in afternoon X 1 + 1 44. The real charge of this plate is to its computed, supposing the el. to spread 07 inc., as 2.89 to 1. The charge of this plate is the same as that of a glass one 345 thick, supposing ratio of real and computed charge the same as in A or B. 679] The coatings being taken from this plate it was included between the plates B and H, and the outside surfaces coated with circles of 6.6 in diam. 552, P. 83, it cont. 6.9 inc. el. less than K, 6.5 5 2 less than D + E + F, by mean it contains 75.5 glob. inc. The charge of plate glass of the same sort as Nairne's 634 thick (id est, equal to the sum of the thicknesses of the two glass plates and a glass plate equiv. to the rosin) = 73.3, supposing the el. to spread the same on this plate as on the rosin. * [Arts. 379, 534.] + [Arts. 381, 552.] |