n6 MICHAEL FARADAY
spermaceti the charge was not equally divided. The instru-
ment with these solid materials took more than half the
charge. Hence the shellac, or dielectric, had absorbed
some electricity. He found that the dielectric took time to
absorb this electricity. When the inner sphere was dis-
charged the electricity slowly came out of the charged
dielectric and began to charge the sphere again. Thus he
had proved that the medium .between conductors, unlike
the medium between gravitating bodies, can affect the forces
acting between the conductors. Faraday's discovery of
"specific inductive capacity" is an interesting example of
his power, because the phenomenon" had previously been
discovered by Cavendish -but1. not published. Faraday
repeated the discovery in order to establish his conception
of electric action. This achievement shows a certain
inevitability in his researches and how he obtained results
independent of luck. His detailed investigation of static
electrical induction shaped in his mind certain conceptions
of its nature. "Induction appears to be essentially an action
of contiguous particles, through the intermediation of which
the electric force, originating or appearing at a certain place,
is propagated to or sustained at a distance, appearing there
as a force of the same kind exactly equal in amount but
opposite in its direction and tendencies/* Then he writes
that "The direct inductive force, which may be conceived
to be exerted in lines between the two limiting and charged
conducting surfaces, is accompanied by a lateral or trans-
verse force, equivalent to a dilation or repulsion of these
representative lines/' a conclusion he had drawn from an
experiment in which he had found that "the induction
fairly turned a corner/' He imagined the curved lines of
the electric field by analogy with the curved lines of the
magnetic field. The electrical researches published by
Faraday in 1838 occupy 143 pages of his Experimental
Researches. Besides the innumerable experiments on the
nature of electric forces, there is a detailed investigation of
brush discharges, and the discovery of the dark discharge
from the cathode in air at low pressure is described.
After these stupendous labours Faraday's health broke