184 J. MORISON : ADDRESS 



their existence is not well established, or they appear, like 

 polonium for instance, to be derivation-products of one of the 

 four radio-active elements I have mentioned. Radium appears 

 to be the most active of these bodies ; indeed, Professor 

 Rutherford estimates its energy to be no less than three million 

 times the energy of uranium. All these radio-active elements 

 have very high atomic weights, and it has been thought that 

 the comparatively large size and complexity of constitution of 

 their atoms may render them specially unstable. The atomic 

 weight of radium is estimated to be about 225. The element 

 itself has never been isolated : we know it only in the form of 

 its salts, such as the chloride or bromide. When we speak of 

 radium it must be understood that its salts are meant. Radium 

 is phosphorescent in the dark, and is continually emitting rays 

 of a peculiarly penetrating character ; and it is also constantly 

 giving out energy in the form of heat. The heat which it emits 

 is suiEcient to keep its temperature permanently raised 5° F. 

 above the temperature of surrounding objects. It has been 

 estimated that one gramme of radium would melt its own 

 weight of ice in one hour and would continue to do so every 

 hour for at least 1,300 years. The rays proceeding from radium 

 have great power of penetration. If a glass tube containing 

 a mere speck of a radium salt be allowed to touch the forehead 

 a sensation of light will be produced. This is due to the rays 

 from radium passing through the glass, through skin, bone, 

 and other tissues, impinging on the retina, and rendering it 

 phosphorescent. There are various chemical effects produced 

 by the radium rays. If a radium salt be dissolved in water, 

 the water is continually though slowly decomposed into its 

 elementary constituents, oxygen and hydrogen, which are 

 evolved in minute bubbles. The radium rays act on a photo- 

 graphic plate in the same manner as light. The physiological 

 eifects of radium are very powerful. Becquerel carried a small 

 piece of a radium salt in his waistcoat pocket for a short time. 

 The skin under the pocket became inflamed, and a painful sore 

 developed, which healed with great difficulty. According to 

 Strutt cases have been reported where the action of radium has 

 resulted in the reduction of cancer growths. He also says that 

 the rays seem to retard the growth of bacteria under certain 

 circumstances and that they destroy the leaves of plants. 



The rays which proceed from radium are of at least three 

 different kinds, which have been called the «, ji, and 7 rays. 

 The rt rays have comparatively little penetrating power, they 



