As to the nature of the Röntgen rays, Professor Wright is inclined
to regard them as a mode of motion through the ether, in longitudinal
stresses; and he thinks that, while they are in many ways similar to
the rays discovered by Lenard a year or so ago, they still present
important characteristics of their own. It may be, he thinks, that the
Röntgen rays are the ordinary cathode rays produced in a Crookes tube,
filtered, if one may so express it, of the metallic particles carried
in their electrical stream from the metal terminal, on passing through
the glass. It is well known that the metal terminals of a Crookes tube
are steadily worn away while the current is passing; so much so that
sometimes portions of the interior of the tube become coated with a
metallic deposit almost mirror-like.

As to the future, Professor Wright feels convinced that important
results will be achieved in surgery and medicine by the use of these
new rays, while in physical science they point to an entirely new
field of investigation. The most necessary thing now is to find some
means of producing streams of Röntgen rays of greater volume and
intensity, so as to make possible greater penetration and distinctness
in the images. Thus far only small Crookes tubes have been used, and
much is to be expected when larger ones become available; but there
is great difficulty in the manufacture of them. It might be possible,
Professor Wright thinks, to get good results by using, instead of the
Crookes tube, a large sphere of aluminium, which is more transparent
to the new rays than glass and possesses considerable strength. It is
a delicate question, however, whether the increased thickness of metal
necessary to resist the air pressure upon a vacuum would not offset
the advantage gained from the greater size. Moreover, it is a matter
for experiment still to determine, what kind of an electric current