screen the action is slower, but it still takes place even through
thick folds, therefore, radiographs can be taken and in this way it
is being utilized by surgery to view the anatomy, the internal organs,
and locate bullets and other foreign substances in the system.

A glass vessel containing radium spontaneously charges itself with
electricity. If the glass has a weak spot, a scratch say, an electric
spark is produced at that point and the vessel crumbles, just like a
Leyden jar when overcharged.

Radium liberates heat spontaneously and continuously. A solid salt of
radium develops such an amount of heat that to every single gram there
is an emission of one hundred calories per hour, in other words, radium
can melt its weight in ice in the time of one hour.

As a result of its emission of heat radium has always a temperature
higher by several degrees than its surroundings.

When a solution of a radium salt is placed in a closed vessel the
radio-activity in part leaves the solution and distributes itself
through the vessel, the sides of which become radio-active and luminous.

Radium acts upon the chemical constituents of glass, porcelain and
paper, giving them a violet tinge, changes white phosphorous into
yellow, oxygen into ozone and produces many other curious chemical
changes.

We have said that it can serve the surgeon in physical examinations
of the body after the manner of X-rays. It has not, however, been much
employed in this direction owing to its scarcity and prohibitive price.