[Illustration: FIG. 21.--PRESSURE = 0.001 MM. = 1.3 M.]

Passing to the next phenomenon, I proceed to show the production of
mechanical energy in a tube without internal poles. It is shown in
Fig. 21 (P = 0.001 millimeter, or 1.3 M). It contains a light wheel of
aluminum, carrying vanes of transparent mica, the poles, A B, being in
such a position outside that the molecular focus falls upon the vanes
on one side only. The bulb is placed in the lantern and the image is
projected on the screen; if I now pass the current, you see the wheels
rotate rapidly, reversing in direction as I reverse the current.

Here is an apparatus (Fig. 22) which shows that the residual gaseous
molecules when brought to a focus produce heat. It consists of a glass
tube with a bulb blown at one end and a small bundle of carbon wool,
C, fixed in the center, and exhausted to a pressure of 0.000076
millimeter, or 0.1 M. The negative electrode, A, is formed by coating
part of the outside of the bulb with silver, and it is in such a
position that the focus of rays falls upon the carbon wool. The
positive electrode, B, is an outer coating at the other end of the
tube. I pass the current, and those who are close may see the bright
sparks of carbon raised to incandescence by the impact of the
molecular stream.

You thus have seen that all the old "radiant matter" effects can be
produced in tubes containing no metallic electrodes to volatilize. It
may be suggested that the sides of the tube in contact with the
outside poles become electrodes in this case, and that particles of
the glass itself may be torn off and projected across, and so produce
the effects. This is a strong argument, which fortunately can be
tested by experiment. In the case of this tube (Fig. 23, P = 0.00068