ness with which Kennedy moved now.

"In ordinary times," began Kennedy, noting as he spoke the outward
attitude of our guests toward each other, "the world would have stood
aghast at the disappearance of such a masterpiece as the Fete by
Watteau. It would have ranked with the theft of Gainesborough's Duchess
of Devonshire, Da Vinci's Mona Lisa, the brown-skinned Madonna of the
Mexican convent, Millet's Goose-girl, and the Shepherd and Flock, the
portrait of Saskia by Rembrandt, and other stolen masterpieces.

"But today the vicissitudes of works of art in war time pass almost
unnoticed. Still there is a fascination exercised over the human mind by
works of art and other objects of historic interest, the more so because
the taking of art treasures seems to have become epidemic in northern
Europe."

He laid down what looked more like two rough sketches than photographs,
yet they were photographs, though the relative brightness of color in
photographs was quite different. Outlines were displaced, also. Ugly
spots and bands marred the general effect. They were peculiar.

"They are X-ray images or radiographs of two oil paintings, both claimed
to be copies of Watteau's famous Fete," explained Kennedy, picking up
one of them.

"In a radiograph of the body," he continued, "the difference of
brightness that distinguishes the heart from the lungs, bones from
flesh, is due to the different densities of tissues. In these pictures
the same effect is produced by the different densities of the pigments,
especially of their principal and heaviest elements."

He paused and laid down a chart. "For anyone who doubts what I am about
to prove, I have made a scale of oil colors arranged in accordance to
their transparency to Roentgen rays by applying standard pigments to
canvas in patches of equal thickness.

"I think you can see what I am driving at. For instance, a design drawn
in a heavy pigment will show through a layer of a less dense pigment,
under the influence of the X-ray--just as bones show through flesh. In
other words, an ordinary photograph reproduces only the surface of a
painting. A radiograph represents all the pigments underneath, also
producing effects in proportion to their densities.

"Let me show you the practical result of all this in studying such
radiographs, as worked out by a German student. I have made several very
interesting and conclusive discoveries which these radiographs I have
taken illustrate."