495] To see whether the machine used for trying Leyden vials* conducted fast. The heavy and light paper cylinders being both hung to conducting wire, and globe turned till heavy ones separated, the light ones closed in 1'. 1" after the others when the conducting wire communicated with machine, and about 1'. 20" when it did not. 496] The plate covered with solut. lac was undone, and that and the plate not varnished were lacquered in Nairne's manner, one with vermillion, the other without. Neither of them were dried after the operation. The old Lac and vermillion and the transparent varnish were dried before fire, heat uncertain. Frid. Oct. 16 [1772]. Th. 63. N. 20. C.-10. The two plates lacquered in Nairne's manner discharged the electricity of the jars presently. Lac and verm. in 1st manner closed in about 10". Sat. Oct. 17 [1772]. The last varnished plates being dried before fire. Th. 05. N. 21. C. – 7. 1st lac and vermil. closed in 2" or 3", did not sep. in 1'. 2 D° closed rather sooner. Transparent closed and sep. again in about 4". Tu. Oct. 19 [1773]. The varnished glasses were baked over stove, the heat being kept for 2 hours at about 170. Wed. Oct. 20 [1773]. Th. 64. N. 22. C. - 5. Lac & verm. closed in about 15". Old lac & verm. Do. Transparent in 1 or 2′′. Do rubbed with cloth, closed and sep. again in 1 or 2". On Wednesday, the varnished plates were baked for above 2 hours, the heat the greatest part of the time about 210, but part of the time the rose a little way into the ball. I suppose must be at least 235 or 240. Fr. Th. 60. N. 22. C. - 5. Transparent closed and sep. again immed. Last lac & verm. closed & sep. again almost immed. 1st Do closed and sep. again in about 2′′. 497] Glasses for exper. on spreading of elect. 9 plates of English glass & 8 of Nuremberg coated with plates of same size. Sun. Oct. 24 [1773]. Th. 63. Comm. - 6. N. 211. + [Of electrical machine. See Arts. 248, 563, 568, 569.] 5 D° 4, 3, 2, 1 Do 1 did not sep. in 1'. N 8 closed and sep. again in less than 2" but did not sep, much. 7 closed in 1 or 2" but did not sep. again soon. 6 closed presently and sep. again more than 8. 5, 4, 3, 2, 1 Do but seemed to sep. at first, to sep. more before it began to close, it was pos. after closing. Sun. & Mon. N 1, 2, 3, 4 & 8 were baked with heat from 130 to 200. The tinfoil of the lowest plate was blistered. Sun. Th. 62. Com. - 15. N. 18. E 2, 3, 4, 5 closed in about 2", 2 and 3 sep. again in 30 or 4[0]. E 1 closed not quite so fast. E 9 not baked closed in about 7", 7 & 6 in about 4", & 8 in about 3". The 5 baked Nuremberg immediately separated wide, some without closing first, others with. N 6 closed and sep. almost immediately, 7 closed and sep. almost immed. but did not sep. wide. 5 closed and sep. again in 5′′ or 7′′. N 8 washed with spts of wine did not close so soon as before. N 8 & E 4 were washed with sp wine & a little ros. varnish & then varnished with rosin. Sun, eve. Th. 60. Com. 20. N. 16. E. 4 did not close in 1'. N. 8 closed in 2 or 3". N. 3 closed and sep. again immed. N. 8 & E. 4 were then cased in soft cement. The plates N. 1 & E. 3 were varnished with lac varnish, & the plates N. 2 & E. 2 with a mixture of 6 parts of varnish & 1 of vermilion, & afterwards baked for about 5 hours with a heat part of the time up to 200, and most of the time above 150, & N. 3 & E. 5 were varnished in the same manner, and then cased in a cement composed of 14 of rosin to 12 of brick dust. N.B. E. 5 was heated in drying the varnish to a great degree, so as to make it smoke violently. Wed. Nov. 4 [1772]. Th. 59. N. 161. C. - 18. E. 4 closed in about 4". E. 5 in 3" or 4". N. 8 closed and sep. again in 3 or 4". N. 3 seemed to do the same rather sooner. Fr. Nov. 6 [1772], the plates E. 1 and N. 4 were varnished with rosin and the plates E. 2 & N. 2 varnished with a mixture of 4 parts of rosin varnish to 1 of vermilion & afterwards baked. They were a good deal heated both in varnishing and baking, so as to be somewhat blistered. The plates E. 3 & N. 1 were also varnished before then and dried before fire. Sat. Nov. 7 [1772]. N. 5 and E. 8 were varnished with rosin, and N. 6 and E. 6 varnished with 8 parts of solut. rosin & 3 of vermilion, and then baked for about 2 hours with heat which part of the time rose to 146, but commonly did not exceed 130. E. 8 closed and sep. again in 2 or 3" about 1 inch. E. 2 Do. E. 1 closed and sep. again in about l'. E. 5 closed in about 2′′. E. 4 did not close in min. 498] Order in which the elect. spread. N 6 rosin & verm. last done 8 in soft cem. 5 & 3 4, 2, 1 (varnished with ros. last done and hard cem. frosin alone, 2 1st rosin and verm. 1st Th. Nov. 4 soft cement E 6 rosin and verm. last done 5 hard cem. 8 rosin last done 1 rosin alone 2 & 3 ros. and verm. 1st ros. alone 1st 4.21 of the lac varnish contains 12 gra. of lac. Th. 58. Com. 13. N. 19. N. 8 in soft cem. closed almost immed. sep. again in 3 or 4". E. 4 in Do did not quite close in min. E. 8 in ros. closed and sep. again almost immed. E. 6 ros. and verm. closed and sep. wide immed. N. 5 ros. more so. N. 6 ros. & verm. same as E. 6. Th. Nov. Th. 58. Com.-7. N. 21. E. 4 at first approached a little nearer, afterwards did not. N. 8 closed and sep. again in about 3′′. E. 2 Lac and verm. closed and sep. wide immed. E. 3 Lac. not so soon. N. 2 Lac and verm. rather quicker. N. 1 Lac. Do. * [Probably Nov. 8, 1772. See Note to Art. 502.] 500] COATED PLATES. 249 E. 1 not varn. closed in about 8". N. 4 closed and sep. again in about 2′′. 499] Sat. Nov. E. 8 & N. 5 were varnished with ros. & E. 6 & N. 6 were varnished with 8 parts of solut. rosin & 3 of vermillion. They were afterwards baked over boiling water for about 2 hours, the heat between 115 & 120. Sun. Nov. E. 1 & N. 4 were varnished with 60 of thick solut. lac, 3.3 of verm. & 19 of spts, and E. 2 & N. 1 were varnished with 60 of solut. lac, 4·16 of verm. & 9 of sp. The quantity of this last mixture spread on the glasses was 8.0. N. 2 not covered, closed rather sooner and sep. rather more than Two trial plates were made with two plates of glass with rosin between, for comparing thick rosin with the double plates A and B. Two trial plates were also made on a piece of the white plate glass for comparing N and thin white with D + E. * [See Arts. 370, 371.] 501] Sat. Oct. 17 [1772]. Th. 65. N. 21. C. 7. Hence it should seem that the plate D contained about 16 inc. el. less than the plates E or G, which is nearly conformable to p. 26, 1772 [Art 489]. The thick rosin plate seems to contain just the same as doub. pl. B, and the 2nd rosin plate to contain 2:49 inc. el. less than D. The thick white seemed to contain 79 inc. el. less than D. 502] Q and P compared with M and K of Nairne, also green cylinder L and white cylinder compared with plates of Nairne by means of sliding trial plates. Mon. Oct. 18*. Th. 64. N. 173. C.-15. [13 observations, Art. 660.] [Result.] Therefore K seems to contain 5 inc. el. less than M, conformable to 1772, p. 26 [Art. 489]. Q contains 16 inc. less, and P 16 less. The comp. power of white cyl. 537.5, and [it] appears to contain 756 inc. el. Therefore inc. el. by comp. power = 1·41. * [As the records of the actual observations in the following articles are of precisely the same nature as those already given, they will be omitted, and as the author has summed up the results for each day, these statements only will be given, except in cases of more than ordinary importance. According to the day of the week and month the dates for these experiments should belong to 1773, but as the experiments seem continuous with those of dates before and after which are certainly in 1772, I think Cavendish made a mistake in the day of the month which he did not find out till 4th November.] |