The study of radioactivity was pursued with great ability not only by the Curies and A.
It requires a radium salt of high radioactivity to be at all comparable in effectiveness with a good water-dropper.
In connexion with the modern study of radioactivity, the electroscope has become an instrument of great usefulness, far outrivalling the spectroscope in sensibility.
This research opened a way of approach to the phenomena of radioactivity, and the history of the steps by' hich P. Curie and Madame Curie were finally led to the discovery of radium is one of the most fascinating chapters in the history of science.
The study of radium and radioactivity led before long to the further remarkable knowledge that these so-called radioactive materials project into surrounding space particles or corpuscles, some of which are identical with those projected from the cathode in a high vacuum tube, together with others of a different nature.