in 1837 reduced, in his opinion, this point of demonstration.
He then found that he could electrify, by induction, an insulated
sphere placed completely in the shadow of a body which screened it
from direct action. He pictured the lines of electric force bending
round the edges of the screen, and reuniting on the other side of it;
and he proved that in many cases the augmentation of the distance
between his insulated sphere and the inducing body, instead of
lessening, increased the charge of the sphere. This he ascribed to
the coalescence of the lines of electric force at some distance
behind the screen.

Faraday's theoretic views on this subject have not received general
acceptance, but they drove him to experiment, and experiment with
him was always prolific of results. By suitable arrangements he
placed a metallic sphere in the middle of a large hollow sphere,
leaving a space of something more than half an inch between them.
The interior sphere was insulated, the external one uninsulated.
To the former he communicated a definite charge of electricity.
It acted by induction upon the concave surface of the latter, and he
examined how this act of induction was effected by placing insulators
of various kinds between the two spheres. He tried gases, liquids,
and solids, but the solids alone gave him positive results.
He constructed two instruments of the foregoing description, equal in
size and similar in form. The interior sphere of each communicated
with the external air by a brass stem ending in a knob.
The apparatus was virtually a Leyden jar, the two coatings of which
were the two spheres, with a thick and variable insulator between
them. The amount of charge in each jar was determined by bringing a
proof-plane into contact with its knob and measuring by a torsion
balance the charge taken away. He first charged one of his