could be easily studied. Accordingly I prepared a tube about 1 inch in
diameter and 1 metre long, with outside coating at each end. The tube
was exhausted to a point at which by a little working the thread
discharge could be obtained. It must be remarked here that the general
aspect of the tube, and the degree of exhaustion, are quite different
than when ordinary low frequency currents are used. As it was found
preferable to work with one terminal, the tube prepared was suspended
from the end of a wire connected to the terminal, the tinfoil coating
being connected to the wire, and to the lower coating sometimes a
small insulated plate was attached. When the thread was formed it
extended through the upper part of the tube and lost itself in the
lower end. If it possessed rigidity it resembled, not exactly an
elastic cord stretched tight between two supports, but a cord
suspended from a height with a small weight attached at the end. When
the finger or a magnet was approached to the upper end of the luminous
thread, it could be brought locally out of position by electrostatic
or magnetic action; and when the disturbing object was very quickly
removed, an analogous result was produced, as though a suspended cord
would be displaced and quickly released near the point of suspension.
In doing this the luminous thread was set in vibration, and two very
sharply marked nodes, and a third indistinct one, were formed. The
vibration, once set up, continued for fully eight minutes, dying
gradually out. The speed of the vibration often varied perceptibly,
and it could be observed that the electrostatic attraction of the
glass affected the vibrating thread; but it was clear that the
electrostatic action was not the cause of the vibration, for the
thread was most generally stationary, and could always be set in
vibration by passing the finger quickly near the upper part of the
tube. With a magnet the thread could be split in two and both parts
vibrated. By approaching the hand to the lower coating of the tube, or
insulated plate if attached, the vibration was quickened; also, as far
as I could see, by raising the potential or frequency. Thus, either
increasing the frequency or passing a stronger discharge of the same
frequency corresponded to a tightening of the cord. I did not obtain
any experimental evidence with condenser discharges. A luminous band
excited in a bulb by repeated discharges of a Leyden jar must possess
rigidity, and if deformed and suddenly released should vibrate. But
probably the amount of vibrating matter is so small that in spite of
the extreme speed the inertia cannot prominently assert itself.
Besides, the observation in such a case is rendered extremely
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