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

light paper just separated

Lane's discharged at 2.0

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 more. 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.

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.

Tu. Mar. 30 [1773]. Th. 56. N. 8.

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 inches square and 2 thick. The outer box was 14 inches square and 4 thick on the outside, and 13 square and 3-4 thick within.

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

[Exp. II. Art. 235.]

[Charge of 2nd thermometer tube 675, jar 1+ jar 2=6234, by Art. 506.]

+ [Exp. I. Art. 218.]

80.7 glob. inc. = 124·3 circ. inc., by Art.

the redundant fluid in the globe had been so much as of that in the hemispheres, I must have perceived it.

As it might be suspected that in the principal experiment the neighbourhood of the hemispheres communicating with [the] ground would enable the globe to hold more than it would otherwise do, and that therefore the cork balls would not separate so much as they would do if the hemispheres were taken away and the quantity of redundant fluid in the globe was the same, and consequently that the above computation of the quantity I could perceive is not just, I took away the hemispheres, made the corks touch the globe, and electrified it till they separated, then holding the hemispheres in my hands as near the globe as in the experiment, I did not perceive any alteration in the separation of the corks.

The outside diameter of the hemispheres was 13.3 inches.

563] Experiment to see whether the force with which two bodies repel is as the square of the redundant fluid in them*: tried with straw electrometer and glass globes.

The two electrometers were hung at opposite ends of a horizontal stick of wood 43 inches long, supported on sticks of waxed glass and communicating near the middle with one of the globest. The same string also which lifted up the electrifying wire let down a piece of wood for making a communication between the two globes. The board with divisions was placed 6 inches behind the electrometers, and the guide for the eye 30 inches before it.

The electricity of the globes wasted very slowly, so that it could not be sensibly diminished in the time between reading off divisions to heavy electrometer and those to light one.

The electrifying wire rested on horizontal wood while globet was turned, two jars being used as a magazine to prevent the globe Leyden vial from charging too fast. The globe was turned till the heavy electrometer separated to rather more than the intended division, after which I waited till it came right, when by the string I lifted up the electrifying wire and made the communication between the two globes and looked at the division of light electrometer. The electricity of the magazine was discharged as soon as the electrifying wire was lifted up.

564] One of the straws used for the heavy electrometer was black in some places, and is called "blighted," the other is called "fair."

[See Art. 386.]

[The coated globes 2 and 3. Their charges are given in Art. 505 as 1782 and 1555 circ. inc., or 1159 and 1009 glob. inc., the sum of which, 2168, agrees with Art. 391.]

[Of Nairne's electrical machine.]

The additional wire was run into straw very easily, and was fastened by putting a little wax on the end, which by heat was pressed quite smooth against the end of the straw.

Mon. morn. Jan. 25. Th. 55. N. 201.

The globe 3 was made to communicate with horizontal wood, then if

heavy electrometer separated to

{

8

9 divisions, the light electrometer (10

separated, on communicating electricity to globe 2, to the same number of divisions.

565] Trials of time in which the electricity of jar 1 was diminished by these straws from degree in which the heavy electrometer used in former experiments of this kind to that in which the pith balls began to close.

In the afternoon the blighted straw was by mistake for the other covered for an hour with paper soaked in salt water. After standing about an hour to dry, it was found that when heavy electrometer was made to separate 10 divisions, light separated 111.

blighted The straw discharged the electricity as before in fair of blighted straw 17.8.

5"

22'

weight

The fair straw was then kept in salted paper in the same manner for about 3 hours.

Tu. morning. Th. 57. N. 23.

If heavy electrometer separates to 15, 10, 9, 8, light electrometer separates about less.

Fair straw discharged the electricity almost immediately, blighted in about 5".

When fair straw rested on cork ball it was about 30", the blighted was much longer.