Heat nor cold do not affect its radioactivity in the least. It gives off but little light, its luminosity being largely due to the stimulation of the impurities in the radium by the powerful but invisible radium rays. Radium stimulates powerfully various mineral and chemical substances near which it is placed. It is an infallible test of the genuineness of the diamond. The genuine diamond phosphoresces strongly when brought into juxtaposition, but the paste or imitation one glows not at all. It is seen that the study of the properties of radium is of great interest. This is true also of the two other elements found in the ores of uranium and thorium, viz., polonium and actinium. Polonium, so-called, in honor of the native land of Mme. Curie, is just as active as radium when first extracted from the pitchblende but its energy soon lessens and finally it becomes inert, hence there has been little experimenting or investigation. The same may be said of actinium. The process of obtaining radium from pitchblende is most tedious and laborious and requires much patience. The residue of the pitchblende from which uranium has been extracted by fusion with sodium carbonate and solution in dilute sulphuric acid, contains the radium along with other metals, and is boiled with concentrated sodium carbonate solution, and the solution of the residue in hydrochloric acid precipitated with sulphuric acid. The insoluble barium and radium sulphates, after being converted into chlorides or bromides, are separated by repeated fractional crystallization. One kilogram of impure radium bromide is obtained from a ton of pitchblende residue after processes continued for about three months during which time, five tons of chemicals and fifty tons of rinsing water are used. As has been said the element has never been isolated or separated in its metallic or pure state and most of the compounds are impure. Radium banks have been established in London, Paris and New York. Whenever radium is employed in surgery for an operation about fifty milligrams are required at least and the banks let out the amount for about $200 a day. If purchased the price for this amount would be $4,000. CHAPTER IV MOVING PICTURES Photographing Motion--Edison's Kinetoscope--Lumiere's Cinematographe--Before the Camera--The Mission of the Moving Picture.