as shown in the illustration on this page. This arrangement of the
apparatus has the advantage of making it much easier to regulate the
electric supply and to modify its intensity, and Dr. Morton finds that
in this way large vacuum tubes, perhaps twenty inches in diameter,
may be excited to the point of doing practical work without danger of
breaking the glass walls. But certain precautions are necessary. When
he uses tin-foil electrodes on the outside of the bulb, he protects
the tin-foil edges, and, what is more essential, uses extremely small
Leyden jars and a short spark gap between the poles of the discharging
rods. The philosophy of this is, that the smaller the jars, the
greater their number of oscillations per second (easily fifteen
million, according to Dr. Lodge's computations), the shorter the wave
length, and, therefore, the greater the intensity of effects.

[Illustration: A GROUP OF FAMILIAR ARTICLES UNDER THE RÖNTGEN RAYS.

From a photograph by Professor Arthur W. Wright of Yale College, taken
through an ebonite plate-holder with fifty-five minutes exposure. It
shows a pair of spectacles in their leather case; an awl and a saw,
with the iron stem, plainly visible through the wooden handles; a
magnifying-glass; and a combination wooden tool-handle with metallic
tools stored in the head, and the metallic clamp visible through the
lower half.]

The next step was to bring more energy into play, still using Leyden
jars; and for this purpose Dr. Morton placed within the circuit
between the jars a Tesla oscillating coil. He was thus able to use in
his shadow pictures the most powerful sparks the machine was capable
of producing (twelve inches), sending the Leyden-jar discharge through
the primary of the coil, and employing for the excitation of the