The facts of radio-activity alone demonstrate the truth of the atomic theory.

To my mind radio-activity is a real disease of matter.

The instrument available for radio-activity measurements is a modified type of the old gold-leaf electroscope.

So it is that we know radio-activity to-day.

He has taken the electrical work in hand with all its modern interest of association with radio-activity.

A little later we detected the continent-wide pattern of radio-activity that had been buried in the rock.

We stand to-day towards radio-activity as our ancestor stood towards fire before he had learnt to make it.

Radium, as we understand it in any of its compounds, can communicate its property of radio-activity to other bodies.

The energy of radio-activity is due to chemical change, but clearly to no chemical change hitherto familiar to science.

For example, the decomposition, or radio-activity, of certain elements prepares one to believe that all elements may exhibit it.

Thus radio-activity is a property of the element, and is not affected by its state of isolation or chemical combination.

No attenuation of "matter" into movement or energy or magnetic radio-activity can reach the impregnable citadel of life.

Thus radio-activity is an atomic property dependent on the amount of an element and independent of its state of chemical combination.

But the discovery of the property of radio-activity has raised many other interesting questions, besides that which we have just dealt with.

From the first detection of radio-activity to its first subjugation to human purpose measured little more than a quarter of a century.

Sir Angus McCurdie, the hard, metallic apostle of radio-activity, glanced for a moment out of the window at the grey, frost-bitten fields.