of these investigations, from the observation of many phenomena I have
gained the conviction that these frequencies would be much lower than
one is apt to estimate at first. In a flame we set up light vibrations
by causing molecules, or atoms, to collide. But what is the ratio of
the frequency of the collisions and that of the vibrations set up?
Certainly it must be incomparably smaller than that of the knocks of
the bell and the sound vibrations, or that of the discharges and the
oscillations of the condenser. We may cause the molecules of the gas
to collide by the use of alternate electric impulses of high
frequency, and so we may imitate the process in a flame; and from
experiments with frequencies which we are now able to obtain, I think
that the result is producible with impulses which are transmissible
through a conductor.

In connection with thoughts of a similar nature, it appeared to me of
great interest to demonstrate the rigidity of a vibrating gaseous
column. Although with such low frequencies as, say 10,000 per second,
which I was able to obtain without difficulty from a specially
constructed alternator, the task looked discouraging at first, I made
a series of experiments. The trials with air at ordinary pressure led
to no result, but with air moderately rarefied I obtain what I think
to be an unmistakable experimental evidence of the property sought
for. As a result of this kind might lead able investigators to
conclusions of importance I will describe one of the experiments
performed.

It is well known that when a tube is slightly exhausted the discharge
may be passed through it in the form of a thin luminous thread. When
produced with currents of low frequency, obtained from a coil operated
as usual, this thread is inert. If a magnet be approached to it, the