C.; in one year the temperature of 876,000 grams of water would be raised through 1 deg.

C.; and in 1800 years, which is approximately the half-life period of radium, the temperature of 1,576,800 _kilograms_ of water would be raised through 1 deg.

C.These results may be expressed by saying that if 1 gram (about 15 grains) of radium were kept until half of it had changed into inactive substances, and if the heat spontaneously produced during the changes which occurred were caused to act on water, that quantity of heat would raise the temperature of about 151/2 tons of water from its freezing- to its boiling-point.
Radium compounds send forth three kinds of rays, distinguished as _alpha_, _beta_, and _gamma_ rays.

Experiments have made it extremely probable that the [alpha]-rays are streams of very minute particles, somewhat heavier than atoms of hydrogen, moving at the rate of about 18,000 miles per second; and that the [beta]-rays are streams of much more minute particles, the mass of each of which is about one one-thousandth of the mass of an atom of hydrogen, moving about ten times more rapidly than the [alpha]-particles, that is, moving at the rate of about 180,000 miles per second.

The [gamma]-rays are probably pulsations of the ether, the medium supposed to fill space.