y were placed
on insulated stands; and a wire connected to X (tried both copper and
iron) carried over to the stove about twenty feet distant. When the end
of the wire was rubbed on the stove it gave out splendid sparks. When
permanently connected to the stove, sparks could be drawn from the stove
by a piece of wire held in the hand. The point X of vibrator was now
connected to the gas-pipe and still the sparks could be drawn from the
stove."

. . . . . . . . .

"Put a coil of wire over the end of rod X and passed the ends of spool
through galvanometer without affecting it in any way. Tried a 6-ohm
spool add a 200-ohm. We now tried all the metals, touching each one in
turn to the point X." [Here follows a list of metals and the character
of spark obtained with each.]

. . . . . . . . .

"By increasing the battery from eight to twelve cells we get a spark
when the vibrating magnet is shunted with 3 ohms. Cannot taste the least
shock at B, yet between carbon points the spark is very vivid. As will
be seen, X has no connection with anything. With a glass rod four feet
long, well rubbed with a piece of silk over a hot stove, with a piece
of battery carbon secured to one end, we received vivid sparks into the
carbon when the other end was held in the hand with the handkerchief,
yet the galvanometer, chemical paper, the sense of shock in the tongue,
and a gold-leaf electroscope which would diverge at two feet from a
half-inch spark plate-glass machine were not affected in the least by
it.

"A piece of coal held to the wire showed faint sparks.

"We had a box made thus: whereby two points could be brought together
within a dark box provided with an eyepiece. The points were iron, and
we found the sparks were very irregular. After testing some time two
lead-pencils found more regular and very much more vivid. We then
substituted the graphite points instead of iron." [26]

[Footnote 26: The dark box had micrometer screws for
delicate adjustment of the carbon points, and was thereafter
largely used in this series of investigations for better
study of the spark. When Mr. Edison's experiments were
repeated by Mr. Batchelor, who represented him at the Paris
Exposition of 1881, the dark box was employed for a similar
purpose.]

. . . . . . . . .

After recording a considerable number of other experiments, the
laboratory notes go on to state:

"November 30, 1875. Etheric Fo