Tu. Mar. 23 and Wed. Mar. 24. [43 obs. Art. 649.]

557] Allowance for connecting wires in p. 86. [Art. 554.]

The allowance to be made for the charge of the connecting wires was endeavoured to be found by suspending the two circles of 9.3 inc. horizontally by silk lines at 11 inches distance from each other and finding their charge by means of the forked electrifying wire as in 1772 p. 7 [Art. 472], both when the plates were connected by a wire similar to that used for connecting the rosin plates, and without any connexion. The event was as follows.

Fr. Mar. 26th [1773. 8 obs. See Art. 647.]

Therefore the plates contain about 2 square inc., or 1·41 inc. el. more with the connecting wire than without *.

Sat. Mar. 27 [1773].

It was tried by usual machine whether the 4 rosin plates contained more el. when at a distance than near. The trial plate B id est the largest trial plate used for D & being placed on neg. side.

With a quantity of additional wire to 9 inc. el. the balls sep. pos. when the plates were at as great a distance as possible. When they were placed close together they seemed to require rather more additional wire, and as well as I could judge, a quantity = about inc. el.

one.

558] Excitation of electricity by separating brass plate from glass

Sat. afternoon. Th. 60. N. 9.

The experiment of p. 71 [Art. 541] was repeated. It was found that the brass plate was electrified on lifting up as before, though the plate was not electrified before. But if the plate was first charged and discharged again before the plate was lifted up, it was found to be stronger electrified.

I then took a piece of tinfoil of the same size as the brass plate, with a silk string fastened to it near the edge, and laid it on the glass and

* [See Art. 647.]

lifted it up gently by the silk string. The tinfoil was found to be electrified thereby.

559] Comparison of Henly's, Lane's,

and straw electrometer.

Sun. Mar. 28 [1773]. Th. about 58. N. about 8.

The two conductors of Nairne were placed end to end, and Henly's electrometer placed on that furthest from globe* parallel to conductor and the cork pointing from globe. The four jars were also joined to the usual wire with the straw electrometer hung to it, the wire and jars being placed at such a distance from the conductors that the electricity was found not to flow sensibly from them to the jars.

The globe 3+ was then applied to that conductor nearest the globe and electrified till Henly's electrometer stood at 90o. The globe 3 was then removed from the conductors and its electricity communicated to the jars.

The straw electrometer separated to 2+.

The experiment was repeated several times and was found to agree together pretty well.

The jars were then electrified, they and the straw electrometer standing in the same place, and it was found that Lane's electrometer fastened to one of them discharged at 0.53 with that degree of electrification, the same jar being applied to the conductor and electrified till Henly's electrometer stood at 90°, Lane's discharged at 12:15.

The conductors being then taken away and the jars and straw electrometer placed in usual position, Lane's discharged at 1.17 when straw stood at 2 +3, and at 1+2 when light paper electrometer just separated. The knobs touched at 0.4.

*

[Of Nairne's electrical machine.]

+ [Globes 2 and 3 are glass globes coated as Leyden jars. See Art. 505 for

their charges.]

[For the charges of these jars see Art. 506.]

The globe 3 electrified till Henly stood at 90°, and its electricity communicated to 1, 2, and 3 jars, straw electrometer separated to 2+13. Lane's with that degree of electrification discharged at 1.7.

When Henly's stood at 90°, Lane's discharged at 12.20.

Jar 2 charged till straw electrometer separated to 4, and electricity communicated to jar 1, straw separated to 2 + 1.

When straw electrometer separated to 4

Lane's discharged at 2:0

52

1.19

1.1

560] Excess of redundant fluid on positive side above deficient fluid on negative side in glass plate and plate air &c.*

Mon. Mar. 29th [1773]. Th. 58. N. 7.

The 11 inch plate coated with circles of 8 inches diameter was supported on waxed glass. I charged this by touching the top with a vial charged till the straw electrometer separated to 2 + 3 while I touched the bottom with a wire. At the same time an assistant stood ready with a bent wire in his hand ready to discharge it as soon as I took the jar away, the wire was fastened to a stick of waxed glass and had the pair of cork balls commonly made use of hanging to it, the cork balls separated about 1 inch.

I then charged the jar 4 to the same degree and communicated its electricity to the jars 1 & 2 and touched the upper side of the plate with one of the jars, but without touching the bottom with the wire. The corks separated very nearly the same as before, but of the 2 rather I then charged the jar till the straw electrometer separated to 2 + 2 and diminished its electricity as before, the corks now separated rather less than the first time. The experiment was repeated several times with very nearly the same event.

more.

I could perceive no difference in the separation of the cork balls whether the wire of the jar with which I touched the plate was 17 inches long or only 23.

If the four jars were charged to 2 + 3 and its electricity communicated to globe 3, it was diminished to 2 + 2.

The plate air 4 was charged by jar charged till straw electrometer stood at 20, and if jar 4 was charged to the same degree and its electricity communicated to jar 2, the corks separated the same if bottom was not touched.

With plate air 1 the charge was obliged to be reduced by communi

[See Note 30.]

cating jar 2 to jar 4 to make the same separation when bottom was not touched as when it was.

The same experiment was repeated, only putting a piece of sealing wax with marks on it supported by glass about 2 inches below the corks to serve by way of comparison.

The second column is the distance to which the straw electrometer separated in charging jar with [which] the plate was electrified when the bottom was touched in order that the cork balls should separate equal to marks on wax. The third column is the ratio in which the electricity of the jar was diminished when the bottom was not touched, and the fourth column shews the degree in which the jar was electrified (as expressed by distance to which the electrometer separated) in order that the balls should separate to the required distance.

N.B. The paper of divisions used for the electrometer was different from that used before, but the divisions nearly of same strength. The marks on sealing wax used for compound plate were nearer than those for plate air.

The jars 1, 3 & 4 being charged till straws separated to 3+0 and the electricity communicated to jar 2, they separated to 2+1, and the electricity of jar 2 being destroyed and the electricity of the others again communicated to it, they separated to 1 + 3*.

Therefore diminishing the electricity in ratio of 95 to 126 diminishes distance to which the balls separate in ratio of 126 to 165, or diminishing the electricity in ratio 1.33 to 1 diminishes distance in ratio 1.31 to 1.

Result.

On Monday the excess of redundant fluid on the positive side above deficient fluid on negative side in

of the quantity of electricity which is given to it with the same degree of electrification if the bottom plate is not touched.

561] Fr. Apr. 2 [1773]. Th. about 55. N. about 10.

It was tried whether a parallelepiped box included within another box of the same shape and communicating with it would receive any electricity on electrifying the outer box*.

The experiment was tried just in the same manner as that with the globe in p. 26 [Art. 513]. The inner box was 12 iuches square and 2 The outer box was 14 inches square and 4 thick on the outside, and 13 square and 3.4 thick within.

thick.

The boxes were made of wainscot and well salted. I could not perceive that the inner box was at all over or undercharged, for if I previously electrified the cork balls positively sufficiently to make them separate in touching the inner box, they would separate as much if I previously electrified them negatively in the same degree.

Globe within hollow globe tried againt.

562] Sun. Apr. 4 [1773]. Th. 58. N. 11.

The globe included between the 2 hemispheres was tried again in the same manner, except that the hemispheres were coated with tinfoil and were made to shut closer.

way.

I could not perceive the inner globe to be at all electrified either

In order to see how small a degree of electricity I could perceive this way, I separated the two hemispheres as far as in the experiment, and electrified the 2nd thermometer tube with the same strength of electricity as was used in the experiment, and communicated its electricity to the jars 1 and 2, then touched the inner globe with one of those jars and drew up the cork balls, previously positively electrified, against the globe. I found them to separate very visibly.

I then repeated the experiment in the same manner except that the balls were negatively electrified in the same degree.

The elect. of the thermometer tube was diminished by communicating to the 2 jars in the ratio of 105 to 6339+, or of 1 to 60, so that if