By good fortune, Professor Becquerel used some Uranium
 for these studies. By accident, he found this Uranium
was sending forth rays that had the power to act as the
X-rays,—to penetrate thick and light proof paper, and after
such penetration to affect a photographic plate as the sunlight
 did. He found that his Uranium did this whether or
not it was first exposed to sunlight; in other words that the
sunlight could not in any way be said to be the cause of
these rays.
Uranium had been known to the world for over a hundred
 years. That it possessed this power to emit rays of
this penetrating nature, was something as new asit was
astonishing.
For years, Uranium had been used to color glass,
especially the fine glasses that made much of the specialized
handiwork of the glass makers of Bohemia.
Marie Sklodowski, of Poland, at this time was a student
at the University of Paris doing post graduate work in
physics and in chemistry under Professors Becquerel and
Curie,
The extent and accuracy of her training and the precision
 and clarity of her mind and methods, won for her
the professional respect and regard of her instructors.
Professor Becquerel and the scientific minds of the
University of Paris and of Europe were so impressed with
the importance of knowing what caused the strange rays
Becquere] had found in his Uranium that special work was
planned to discover the secret. Of them, he could learn
only that they were electrical.
Marie Sklodowski was invited to undertake the study
and investigation of the problem, by Professor Becquerel.
She accepted and carried through to completion, what has
since been described as one of the most comprehensive and
conclusive scientific studies of the age.
With characteristic directness, she went first to the
mines from which had been taken the ore that had given
the Uranium to Professor Becquerel. This was called
pitchblende; and, as was known to all the laboratories of
Europe, it was a combination of most of the well known
metals. At these mines, this pitchblende ore was thrown