g a very essential difference, while
their range and penetrative power are incomparably greater. In fact,
all those qualities which have lent a sensational character to the
discovery of Roentgen's rays were mainly absent from these of Lenard,
to the end that, although Roentgen has not been working in an entirely
new field, he has by common accord been freely granted all the honors
of a great discovery.

[Illustration: SKELETON OF A FROG, PHOTOGRAPHED
THROUGH THE FLESH. THE SHADINGS INDICATE, IN ADDITION TO THE BONES,
ALSO THE LUNGS AND THE CEREBRAL LOBES.

From a photograph by Professors Imbert and Bertin-Sans; reproduced
by the courtesy of the "Presse Medicale," Paris. In taking this
photograph the experiment was tried of using a diaphragm interposed
between the Crookes tube and the plate; and the superior clearness
obtained is thought to result from this.]

[Illustration: RAZOR-BLADE PHOTOGRAPHED THROUGH A LEATHER CASE AND THE
RAZOR-HANDLE.

From a photograph taken by Dr. W.L. Robb of Trinity College. The
shading in the picture indicates, what was the actual fact, that the
blade, which was hollow ground, was thinner in the middle than near
the edge.]

[Illustration: SKELETON OF A FISH PHOTOGRAPHED THROUGH THE FLESH.

From a photograph by A.A.C. Swinton, Victoria Street, London.
Exposure, four minutes.]

Exactly what kind of a force Professor Roentgen has discovered he does
not know. As will be seen below, he declines to call it a new kind of
light, or a new form of electricity. He has given it the name of the
X rays. Others speak of it as the Roentgen rays. Thus far its results
only, and not its essence, are known. In the terminology of science it
is generally called "a new mode of motion," or, in other words, a new
force. As to whether it is or not actually a force new to science, or
one of the known forces masquerading under strange conditions, weighty
authorities are already arguing. More than one eminent scientist has
already affected to see in it a key to the great mystery of the law
of gravity. All who have expressed themselves in print have admitted,
with more or less frankness, that, in view of Roentgen's discovery,
science must forth-with revise, possibly to a revolutionary degree,
the long accepted theories concerning the phenomena of light and
sound. That the X rays, in their mode of action, combine a strange
resemblance to both sound and light vibrations, and are destined to
materially affect, if