the same chain which I used in the foregoing experiments, consisting of 25 links, and suspended it by its extremities from the extreme hooks of the machine described in Art. 433, and applying the end of the machine to the negative side of the battery, touched the positive side with a piece of metal held in the other hand, so as to receive the shock through the chain without its passing through the torpedo; the battery being charged to such a degree that the shock was considerably stronger than what I usually felt in the foregoing experiments. I found that if the chain was not stretched by an additional weight, the shock did not pass at all: If it was stretched by hanging a weight of seven pennyweights to the middle link, it passed, and a light was visible between some of the links; but if fourteen pennyweights were hung on, the shock passed without my being able to perceive the least light, though the room was quite dark; the experiment being tried at night, and the candle removed before the battery was discharged*. It appears, therefore, that if in the experiments made by these gentlemen the shock never passed, except when the chain was somewhat tense, which in all probability was the case, the circumstance of their not having perceived any light is by no means repugnant to the supposition that the shock is produced by electricity †.

[Art. 613.]

+ [See note 29 and preface.]

EXPERIMENTS, 1771.

1ST NIGHT*.

438] East plate neg[ative] standing east and west. West plate pos[itive] north and south. East plate touched perpend[icularly] by wire near midd[le]. West wire bearing against north side of west plate.

Position of east and west plates reversed. Plates touched by wires as last time.

[Probably the first trials of the apparatus described in Art. 240].

From the two other nights' experiments it seemed as if the positive bottle electrified the plates sensibly stronger than the negative one: why there was not the same difference this night I cannot tell.

Plates east and west. Wires straight.

441] Two pair of large corks were made, each of which was found to separate with the same force. The weight of one pair of them was then made four times as great by the addition of lead to them.

The quantity of electricity in 3rd made vial was then compared by means of these corks with that of a glass plate with circular coating 2.4 inches in diameter and about 06 thick, by touching the glass 8 or 9 times the electricity was reduced from strength requisite to make heavy corks separate to that requisite to make light corks separate, or was reduced to, therefore the vial should contain 12 times as much electricity as the glass plate and wire by which communication was made, which was about 12 inches long*.

442] Three coated plates were made

Mean 54:34. (D is cased with cement.)

A circular coating 5.39 inches diameter was made to thick plate in place where its thickness seemed 178, therefore its computed power is equal to the sum of foregoing three plates. The proportion of thickness to diameter is nearly the same.

* [See Arts. 413, 582.]

Two sliding coated plates were made for trying the foregoing, the trial plates being electrified negatively, the others positively.

Therefore F seems to contain about as much electricity as C, and D

to contain about more.

444] Three coated plates were made on thick plate each 1.8 inches diameter, the mean thickness of glass being supposed 18, therefore the computed power of all three together = 54.

All 3 plates together

separated pos.

With C

465.]

4

5

did not separate.

N.B. The breadth of the sliding plate is not known. 445] Small sliding plate not drawn out 14 x 9.4.

[This column gives the side of a square equivalent to the trial plate. See Art.

Pasteboard circle 19.4 inches diameter hung on silk strings.

With circle 18 inches diameter on glass 18 thick it separated a little negatively with plate 19 × 19, and would most likely not separate at 19 x 21 or 19 x 22 20 or 203. Therefore quantity of electricity therein most likely is to that of globe as 20-2 to 124 or as 10: 6.

=

446] Thickness of double plate of glass at centre of circle = 285. Diameter of coating = 1.75.

Being tried against small plate not drawn out, separated considerably positive, therefore quantity of electricity therein might perhaps be to that in globe as 11 to 18, and therefore its actual power would be to that of thick plate as 6-6 to 18. The computed power is to that of thick plate as 10-8 to 18.

A coating 145 inches diameter was made on thick plate where the thickness is supposed 168, therefore computed power - 12.5. This being tried against sliding plates was as follows:

=

therefore quantity of electricity therein seems to be to that of globe as 13.7 to 12-6, or 17.4 to 16:3, id est as 14 to 13,

447] The wires placed horizontally and parallel to each other, one end supported by silk, the other by waxed glass.

The trial wire consisted of iron wires 14 thick sliding on each other, supported in [the] same manner.

*

[The charges of the globe and the circle of 194 inches appear from these numbers to be as 28.9 30.7. The diameter of the tin circle, 18.5, was probably calculated from these experiments so that its charge might be equal to that of the globe. The correct diameter would have been 19 inches.]