carbon steel and nickel steel for the purpose of having him test them
with the Röntgen rays, and see if they showed any radical differences
in the crystalline structure. Photographs were taken as desired, but
at the time of my visit only negative results had been obtained.

Dr. Robb realizes the great desirability of finding a stronger source
of Röntgen rays, and has himself begun experimenting with exhaustive
bulbs made of aluminium. One of these he has already finished, and
has obtained some results with it, but not such as are entirely
satisfactory, owing to the great difficulty in obtaining a high vacuum
without special facilities.

I also visited Professor U.I. Pupin of Columbia College, who has been
making numerous experiments with the Röntgen rays, and has produced
at least one very remarkable shadow picture. This is of the hand of
a gentleman resident in New York, who, while on a hunting trip in
England a few months ago, was so unfortunate as to discharge his gun
into his right hand, no less than forty shot lodging in the palm and
fingers. The hand has since healed completely; but the shot remain
in it, the doctors being unable to remove them, because unable to
determine their exact location. The result is that the hand is almost
useless, and often painful.

Hearing of this case, Professor Pupin induced the gentleman to allow
him to attempt a photograph of the hand. He used a Crookes tube. The
distance from the tube to the plate was only five inches, and the hand
lay between. After waiting fifty minutes the plate was examined. Not
only did every bone of the hand show with beautiful distinctness, but
each one of the forty shot was to be seen almost as plainly as if it
lay there on the table; and, most remarkable of all, a number of shot