inutes 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
vacuum tube the "step up" current of the secondary coil with a
potential incalculably increased.

While Dr. Morton has in some of his experiments excited his Leyden
jars from an induction coil, he thinks the best promise lies in the
use of powerful Holtz machines; and he now uses no Leyden jars or
converters, thus greatly adding to the simplicity of operations.

In regard to the bulb, Dr. Morton has tested various kinds of vacuum
tubes, the ordinary Crookes tubes, the Geissler tubes, and has
obtained excellent results from the use of a special vacuum lamp
adapted by himself to the purpose. One of his ingenious expedients
was to turn to use an ordinary radiometer of large bulb, and, having
fitted this with tin-foil electrodes, he found that he was able to
get strongly marked shadow pictures. This application of the Roentgen
principle will commend itself to many students who, being unable to
provide themselves with the rare and expensive Crookes tubes, may
buy a radiometer which will serve their purpose excellently in any
laboratory supply store, the cost being only a few dollars, while the
application of the tin foil electrodes is perfectly simple.

In the-well equipped Jackson laboratory at Trinity College, Hartford,
I found Dr. W.L. Robb, the professor of physics, surrounded by
enthusiastic students, who were assisting him in some experiments with
the new rays. Dr. Robb is the better qualified for this work from
the fact that he pursued his electrical studies at the Wuerzburg
University, in the very laboratory where Professor Roentgen made his
great discovery. The picture reproduced herewith, showing a human foot
inside the shoe, was taken by Dr. Robb. The Crookes tubes used in this
and in most of Dr. Robb's exper