"AN ATTEMPT TO EXPLAIN SOME OF THE PRINCIPAL PHENOMENA OF ELECTRICITY,

BY MEANS OF AN ELASTIC FLUID." From the Philosophical Transactions

for 1771 (p. 1-50).

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

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

67-72

Charge of a thin flat plate independent of its thickness

73

Two parallel circular plates

74-83

Equilibrium of electricity in bodies communicating by a canal is in-

dependent of the form of the canal

84-93

Whether the conditions of equilibrium are the same for two bodies com-

municating by a conducting wire as if they communicated by a canal

of incompressible fluid.

94-96

Molecular constitution of air

97

PART II.

Containing a comparison of the foregoing theory with Experiment.

§ 1. Conductors and non-conductors

Electric properties of air and vacuum

Positive and negative electrification

§ 2. Attraction and repulsion

Electrometer in electrified air

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

to the air.

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

§ 7. Wilcke and Epinus's experiment of electrifying a plate of air

(Mém. Berl. 1756, p. 119)

§ 8. Electric spark.

98

99, 100

101-105

106-117

117

118-126

127

134

135-139

PRELIMINARY PROPOSITIONS.

From the MS. in the possession of the Duke of Devonshire, No. 4.

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. 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 XIII. Repulsion of two columns

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

Cor. Potential of middle and end.

ARTICLES

140

141

142

143

144

145

146

147

148

149

Prop. xxx1 (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

Cor. 8. Charge directly as surface and inversely as thickness

168

Prop. xxxv (Fig. 9). Theory of conducting strata in the glass plate

Prop. xxxvi (Fig. 10). Penetration of glass by fluid

169

170

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

penetration

173

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

lent thickness

174

APPENDIX.

From MS. No. 5.

ARTICLES

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

charged body

175

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

Lemma. Potential of two equal particles compared with that of their

sum at their centre of mass

187

Applied to case of two parallel disks

188

Mutual action of large circle and trial plate in Experiment v.

Mutual action of small circles and trial plate in Experiment v.

189

190

192

Effect of floor and walls of the room

193

Effect of earth connexion the same as if it were infinitely long

194

THOUGHTS CONCERNING ELECTRICITY.

From MS. No. 18. (Probably an early draft of the theory.)

Hypothesis of an electric fluid

195

The fluid acts at a distance but does not itself extend to any perceptible

distance from electrified bodies

196

Proof of this, and objections to the hypothesis of electric atmospheres

On the hypothesis of electric atmospheres.

Definitions of positive and negative electrification, and of over and under

charge.

Fifth hypothesis, on the communication of electricity between conductor

and the surrounding air

208

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

The electricity of glass is here taken to be positive

217

First experiment. A globe within a hollow globe and in communication

with it does not become over or undercharged when the whole is

The charge of the inner globe is less than of that of the outer globe

Hence the electric force is inversely as the square of the distance

Demonstration of this by Lemma 4 (Fig. 13)

Limits between which the law of force must lie, n=2±

Second experiment-A piece of wood within a vessel formed of two

wooden drawers

234

235

(2) EXPERIMENTS ON THE COMPARISON OF CHARGES.

From the MS. Nos, 9 and 10 (apparently prepared for publication).

Intention of the experiments

236

Definition of the ratio of the charges of two bodies, illustrated by the

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

249

250

251

252

253

254

255

255

256

257

258

259

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

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

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

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

long one

279

Comparison with theory

280

Seventh experiment. Comparison of the capacities of several bodies

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

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

288