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 Röntgen 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 Röntgen 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,