path of an electrified molecule may differ from that of one in its
ordinary state.

[Footnote 2: "The thickness of the dark space surrounding the negative
pole is the measure of the mean length of the path of the gaseous
molecules between successive collisions. The electrified molecules are
projected from the negative pole with enormous velocity, varying,
however, with the degree of exhaustion and intensity of the induction
current."--_Phil. Trans._, part i., 1879, par. 530.

"The extra velocity with which the molecules rebound from the excited
negative pole keeps back the more slowly moving molecules which are
advancing toward the pole. The conflict occurs at the boundary of the
dark space, where the luminous margin bears witness to the energy of
the discharge."--_Phil. Trans._, part i., 1879, par. 507.

"Here, then, we see the induction spark actually illuminating the
lines of molecular pressure caused by the excitement of the negative
pole."--_R.I. Lecture_, Friday, April 4, 1879.

"The electrically excited negative pole supplies the _force majeure_,
which entirely, or partially, changes into a rectilinear action the
irregular vibration in all directions."--_Proc. Roy. Soc._, 1880. page
472.

"It is also probable that the absolute velocity of the molecules
is increased so as to make the mean velocity with which they
leave the negative pole greater than that of ordinary gaseous
molecules."--_Phil. Trans._, part ii., 1881, par. 719.]