The radio-activity of the elements in the ore give off the light.
The discovery of radio-activity has revolutionized the ideas of the constitution of matter.
It explains the mysteries of the universe, radio-activity and life.
The substance ranking next in radio-activity to radium is thorium.
The discovery of radio-activity is one of the most momentous in the history of science.
Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905.
It accepted and played with the idea, just as it might have accepted and played with the idea of radio-activity.
There is just a negligible amount of radio-activity present, and no more ultra-violet rays then there are in an average sun lamp.
These are matters, however, on which further light may be thrown as research in radio-activity progresses.
We may here refer to another new conception to which the discovery of radio-activity has given rise.