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Charges of similar bodies as the n-1 power of their corresponding diame-

ters, and independent of the material of which they are made


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Equilibrium of electricity in bodies communicating by a canal is in-
dependent of the form of the canal

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Containing a comparison of the foregoing theory with Experiment.

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§ 3. On the cases in which bodies receive electricity from, or part with it
to the air.

§ 5. Canton's and Franklin's experiments.

99, 100



(Mém. Berl. 1756, p. 119)

§ 8. Electric spark.


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Prop. XXIX (Fig. 1). If the fluid uniformly spread on a circular plate is

to that collected in the circumference as p to 1 the capacity of the

plate is to that of the globe as p+1 to 2p+1

Prop. XXX. Capacity of two disks at a finite distance

Cor. 1. Capacity in terms of p

Cor. 2. Capacity when the density is supposed uniform

Cor. 3. The place in which the canal meets the disk is indifferent only

when the fluid is in equilibrium

Lemma xii (Fig. 2). Repulsion of a particle on a column

Lemma xi. Repulsion of two columns

Lemma xiv.

Lemma xv (Fig. 3). Action of a uniform cylinder on an external point .

Cor. Potential of middle and end.

Prop. XXXI (Fig. 3). Charge of cylinder compared with that of globe

Cor. Upper and lower limits of charge

Prop. XXXII (Fig. 4). Charge of two equal cylinders at a finite distance .

Prop. XXXIII. Ratio of charges of B and b may be deduced from the

ratios of B and b to C.

Lemma xv (Fig. 5). Repulsion on a short column close to an electrified


Lemma xvi (Fig. 6). Two equidistant concave plates

Cor. 1. Definition of corresponding points, &c.

Cor. 2. Density increasing towards the circumference

Lemma xvii (Fig. 7). Concave plate compared with flat one


Prop. XXXIV (Fig. 8). Theory of a coated plate

Cor. 1. Flat coated plate of any form

Cor. 2. Flat circular plate

Cor. 3. Plate not flat but of uniform thickness

Cor. 4. Density increasing towards the circumference

Cor. 5. General conclusion

Cor. 6. Comparison with globe
Cor. 7. Form of plate indifferent .
Cor. 8. Charge directly as surface and inversely as thickness
Prop. xxxv (Fig. 9). Theory of conducting strata in the glass plate
Prop. XXXVI (Fig. 10). Penetration of glass by fluid
Cor. 1. Equivalent thickness of plate if there were no penetration
Cor. 2. Thickness of coatings indifferent.
Prop. XXXVII. Density more nearly uniform than if there had been no

Cor. Distribution probably nearly the same as in plate of air of equiva-

lent thickness


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Prop. 1. Charge of a condenser little affected by the presence of an over-

charged body


Prop. II.

Part 1. A stricter demonstration, applicable to case of penetration

Part II.

Cor. 1

Cor. 2

Cor. 3

Cor. 4. Effect of an overcharged body

Cor. 5.

Cor. 6 (Fig. 11). Two coated plates in communication little affected by

an overcharged body

Cor. 7. Canals may be curved as well as straight
Lemma. Potential of two equal particles compared with that of their

sum at their centre of mass
Applied to case of two parallel disks
Mutual action of large circle and trial plate in Experiment v.
Mutual action of small circles and trial plate in Experiment v.



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Effect of floor and walls of the room
Effect of earth connexion the same as if it were infinitely long

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From the MS. No. 7 (apparently prepared for publication).

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Method of testing

Advantages of the method

Capacity of the trial plate

The gauge electrometer

Form of electrometer used in the later experiments. (Fig. 30)

Estimation of error arising from unequal electrification in the two trials

Comparison of the capacities of two bodies


Why the electrification is tested by the gauge electrometer

The bodies to be tested were chosen of nearly equal capacity

Measurements of the apparatus

The insulating supports of waxed glass. (Fig. 16)

Electrification of air

Effects of the electrification of the air

The earth-connexions

The electrometer threads salted

Leakage of the Leyden vials

Estimate of the accuracy of the experiments

Probable cause of error

Weak charges always used

Reason for this

Third experiment. On the effect of variations in the arrangement of the

apparatus in testing capacities. (Fig. 17)

Six different arrangements

Results of the six arrangements


Fourth experiment. Capacities of bodies of different substances, but of

the same shape and size

Glass coated with various substances

Method of the experiment

Effect of the thickness of a plate on its capacity

Fifth experiment. Charge of two small circles compared with that of a

large one. (Fig. 18)

Results of the experiment

The experiment repeated in a different manner

Comparison with theory

Remarks on the calculation

Bearing on the theory

Sixth experiment. Charge of two short wires compared with that of one

long one

Comparison with theory

Seventh experiment. Comparison of the capacities of several bodies

Comparison of disk with sphere

Comparison of square plate with disk

Oblong plate


Comparison of different cylinders

Disturbing cause

Eighth experiment. Comparison of the charge of the middle plate of

three parallel plates with that of the outer ones. (Fig. 19)

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