501] Sat. Oct. 17 [1772]. Th. 65. N. 21. C. 7.

Plates tried.

D of Nairne

G of N in cem[ent]

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. 171. 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.]

The comp. power of green cyl. is 318.2, and [it] appears to contain 540 × 21 inc. el., therefore inc. el. by comp. power = 1.62*.

503] 1st and 2nd green and white cylinder and white jar compared with H of Nairne in usual manner.

[12 observations.]

[Result.] Hence it should seem that the white cyl. contained as much el. as H; the 2nd green contained 45 inc. el. more than H; the 1st green uncertain, and the white jar seemed to contain 74 inc. el. more.

504] Trials of the same cylinders and jar in same manner except that in trying the white jar and 1st green cylinder the plate M of Nairne was placed on the neg. side as an additional trial plate.

Sat. Dec. 5 [1772]. Th. 56. N. 20.

[13 observations. Art. 660.]

[Result.] Hence 1st green cylinder should cont. 135 inc. el. more than H

By means of this and preceding page, the quant. el., comp. power and quant. el. by comp. power are as follows+:

505] The quant. el. in the 2 coated globes was tried by putting the

white cylinder and the 6th sliding plate on neg. side.

[6 observations.]

[Result.] Therefore globe 2

seems to contain globe 3

(1782

1555 [circ.] inc. el.

Trials of jars used in the 1st sort of experiments: [Art. 240] tried by putting a sliding plate with or without the white cylinder on neg. side.

Th. Dec. 3 [1772]. Th. 55. N. 22.

[6 observations.]

[Result.] There seems some mistake in the 3rd exper., therefore if we make use only of those exper. in which they sep. pos. the jar for (neg. side

pos. side

162
0

contains more than H;

* [These measures of specific inductive capacity must be multiplied by 5·1. See

note to Art. 462.]

+ [See Art. 383.]

inc. of el., but if we made use only of the other exper. it

would be neg. side 1233

side.

pos. side 1043*

506] Trials of the 4 large jars, the jars being placed on the neg.

507] Trials of the 5th and 6th trial plates, the trial plate being placed on neg. side.

Therefore trial plate 6-56=H.

Result.

[Trial plate]

6-18 rather more than C.

By mean 6-18= C, and trial plate 5-17 = C.

The trial plate 4 is on same plate as 5, and the area of one division on it is to that of 5 on trial plate 5 as 1.82 to 9.

508] Thick white, 2nd rosin, D and F of Nairne, and the two double plates together, compared together, also thin white with D and E and D and F.

Sat. Dec. 5 [1772] in evening. Th. 56. N. 28.

[24 observations.]

N.B. Before these exper. were tried, the plates E and F were freed from cem[ent] and coated afresh with plates of same size. The plate D was also freed from the varnish and coated afresh, and the trial plate B was freed from cement and coated with rather larger plates.

Hence it should seem that thick ros. contained 11 inc. el. less than the doub. plates A or B, id est 18.2 inc. el., that the thick white contained same as D, id est 36 inc., and that 2nd ros. contained 2·03 inc. less, id est 34 inc., which differs very little from p. 12 [Art. 501].

M.

509] Whitish plate, P, Q, O, old G and thin rosin compared with

Sun. Dec. 6 [1772]. Th. 54. N. 20.

[19 observations. Art. 655.]

[Result.] By these exper. the two double plates should contain about 1.13 inc. el. more than D, that thick white contained same as D, that the 2nd rosin contained 2.26 less, that the thin white contained 45 less than D+ E, and that N contained 1.81 less.

Sunday evening. Th. 57. N. 17.

[18 observations.]

510] Crown A and C compared with A, B and C of Nairne. Mon. Dec. 7 [1772]. Th. 55. N. 181.

[10 observations.

21 observations of spreading of electricity on the different plates.]

By the above exper. Crown A and C should contain 15 inc. el. less than A.

511] Whether the shock from the plate air was diminished by changing the air between them by moving them horizontally*.

Sat. Dec. 18 [1773 +]. Th. 60°. N. 23.

It was tried whether shock in charging plate air was sensibly diminished by moving the 2 plates horizontally, and thereby changing the air between them in the manner represented in figure, where AB represents the two 8-inch brass plates with sealing wax between them suspended by the silk strings AC and BD.

AE and BF are silk strings fastened to the frame on which lower plate rests, and passing over wire hooks E and F, and stretched by [Probably Dec. 19, 1772. See Art. 502.]

*

[See Arts. 345, 516.]

weights so that the plates would move from E towards F and rest in any position.

The electrifying wire was suspended by the string G with a counterpoise.

The plates were electrified, holding my finger to bottom plate, they were then moved 24 inches by lifting up the weight M, and then discharged by holding my little finger to lower plate and touching upper plate with brass knob held in the other hand. I could feel a small pulse in little finger, having tried this I electrified and discharged the plates in same manner only without moving them first and endeavouring to preserve the same distance of time between the electrification and discharge. I was not able to perceive any difference in the feel. I endeavoured to ascertain the time by the vibrations of a pendulum, but without much success. It seemed needless, however, as I could perceive scarce any difference in the sensation whether I discharged it immediately or waited as long as when the plates were moved. The usual time between the electrification and discharge was about 21".

The experiment was also made by Richard, who did not perceive any difference.

The heavy paper electrometer was used. The bits of sealing wax between the plates were those made in 1771 [Art. 457].

512] Whether globe included within hollow globe is overcharged by electrifying outer globe*.

It was tried whether the globe enclosed within hollow paper globe was overcharged when the outer globe was electrified.

This was first tried by making the 2 hemispheres slide on 2 sticks of glass by means of 2 tin hooks and a stick of glass fixed to the back of the hemisphere.

The wire by which it was elect. was suspended about 4 inches above the hemispheres while the vials were charging. It was then let down, and it was so contrived that the same motion of the hand which lifted up again the elect. wire, lifted up the wire which connected the inner globe with the outer, drew back the hemispheres, and drew up the pith balls fastened to a stick of glass till they touched the inner globe.

It was found that if the elect. of the hemispheres was discharged before they were separated, but after the communication between them and the inner globe was taken away, that the pith balls did not sep., but if they were separated before their elect. was discharged, then the pith balls would at first sep. about an inch or so, but quickly closed, whereas if the inner globe was electrified after the hemispheres were separated, it was found to be a great while before the pith balls closed. It was found that this was owing to the sticks of glass on which the hemispheres slid being electrified thereby, as the same phenomena were produced by electrifying those sticks when the hemispheres were taken off.

* [See Exp. 1. Art, 218.]