for the time being. At the end of several days work was again resumed,
but the plates had been lying so long in the darkroom that they were
deemed almost valueless and it was thought that there would not be
much use in trying to use them. Becquerel was about to throw them away,
but on second consideration thinking that some action might have
possibly taken place in the dark, he resolved to try them. He developed
them and the result was that he obtained better pictures than ever
before. The exposure to sunlight which had been regarded as essential
to the success of the former experiments had really nothing at all to
do with the matter, the essential thing was the presence of uranium
and the photographic effects were not due to X-rays but to the rays
or emanations which Becquerel had thus discovered and which bear his
name.

There were many tedious and difficult steps to take before even our
present knowledge, incomplete as it is, could be reached. However,
Becquerel's fortunate accident of the plate developing was the beginning
of the long series of experiments which led to the discovery of radium
which already has revolutionized some of the most fundamental
conceptions of physics and chemistry.

It is remarkable that we owe the discovery of this wonderful element
to a woman, Mme. Sklodowska Curie, the wife of a French professor and
physicist. Mme. Curie began her work in 1897 with a systematic study
of several minerals containing uranium and thorium and soon discovered
the remarkable fact that there was some agent present more strongly
radio-active than the metal uranium itself. She set herself the task
of finding out this agent and in conjunction with her husband, Professor
Pierre Curie, made many tests and experiments. Finally in the ore of
pitchblende they found not only one but three substances highly