inal, at Rome, compelled bigotry to behold the shining horns of
the crescent Venus, thus opening as if by compulsion the sublime
vista of the heavens and bringing in a new concept of the planetary
and stellar worlds,--no such other discovery as that of the so-called
Roentgen rays has been made. The results which seem likely to flow from
this marvelous revelation surpass the human imagination. Let us try in
a few words to realize the discovery, and define what it is.

It was on the eighth of November, 1895, that Dr. William Konrad
Roentgen, of Wuerzburg, made the discovery which seems likely to
contribute so much to our knowledge of the mysterious processes of
nature. On that day Dr. Roentgen was working with a Crookes tube in his
laboratory. This piece of apparatus is well known to students and
partly known to general readers. It consists of a glass cylinder,
elongated into tubular form, and hermetically closed at the ends. When
the tube is made, the air is exhausted as nearly as possible from it,
and the ends are sealed over a vacuum as perfect as science is able to
produce. Through the two ends, bits of platinum wire are passed at the
time of sealing, so that they project a little within and without. The
interior of the tube is thus a vacuum into which at the two ends
platinum wires extend. Electrical communication with outside apparatus
is thus supplied.

It has long been known that on the discharge of an electrical current
into this kind of vacuum peculiar and interesting phenomena are
produced. The platinum wires at the two ends are connected with the
positive and negative wires or terminals of an induction coil. When
this is done, the electrical current discharged into the vacuum seems
to flash out around the inner surfaces of the tube, in the form of
light. There are brilliant coruscations from one end to the other of
the tube. The tips of the platinum wire constituting the inner poles
glow and seem to flame. That pole which is connected with the positive
side of the battery is called the _anode_, or _upper_ pole, and that
which is connected with the negative, or receptive, side of the
battery, is called the _cathode_, or lower pole. It was in his
experimentation with this apparatus, and in particular in noticing the
results at the cathode or lower end of the tube, that Professor
Roentgen made his famous discovery. It was for this reason that the
name of "cathode rays" has been given to the new radiant force; bu