The following experiments on the brush discharge
have been taken from Nikola Tesla's "Experiments
with Alternate Currents of High Potential and High Fre-
quency."

There is practically nothing except some wire and a few
supports required for all these experiments on the brush
discharge, and thus they can be performed by every one. In
the first experiment two insulated wires about 10 feet long
are stretched across the room. They are supported at dis-
tances of a foot and a half by insulating cords. One of the
wires is attached to each terminal of the coil. When the
coil is put in action the wires are seen to be strongly illumi-
nated by the streams issuing abundantly from their whole
surface. (This experiment must be shown in the dark, of
course.) The cotton covering on the wire, although it may
be very thick, does not affect the result.
To produce the best effect the primary gap and the length
of the wires must be carefully adjusted. It is best to take
the wires at the start very long and then adjust them by
cutting off first long pieces and then shorter and shorter
lengths until the correct length is reached. When this
adjustment has been obtained and the wires are fed by either



86 The Tesla Coil

the 12^^ or 7" coil, the light from them will be sufficient to
distinguish objects in the troom.
