ON ENERGY OF EONTGEN AND BECQUEREL RAYS, ETC. 55 
energy emitted (supposed produced throughout the volume of the substance) is 
absorbed in the substance itself. An approximate determination of the total energy 
per second that can be radiated by 1 gramme of uranium could be determined by 
dissolving a few cin^stals, say, of uranium nitrate in water and pouring the solution 
over a large surface area. On evaporating the water a very thin film of the nitrate 
would be left on its surface. In such a case the rays produced throughout the volume 
of the film shoidd reach the surface without much loss due to absorption, and the 
maximum current through the gas would be proportional to the total energy radiated. 
In this case half of the total energy would be absorbed in the substance on which the 
film was jfiaced and only half would be efiicient in producing ions. 
In order to obtain an approximate value of the total energy of radiation, uranium 
oxide in the form of a very fi]ie dust was spread over a surface of 38 scp centims. 
\Yeight of uranium oxide = ’138 gramme. 
Current = ’02 electrostatic unit. 
Total energy radiated into the gas per second = 1’4 X 10~^° calorie. 
Energy per gramme of uranium oxide radiated into the air 
= 10“^ calorie per second. 
= ‘032 calorie per year. 
Ill our present state of knowledge it is uncertain whether the radiating jiower is 
confined to the surface of the uranium or is given out uniformly throughout the 
mass. In any case, the total energy radiated is probably greater than the value 
above on account of absorption of the radiation in the uranium itself, and also on 
account of the existence of a more penetrating type of radiation, the energy of which, 
has been neglected in the above calculations. 
Energy of Thoi'iurn Radiation. 
The ajiparatus employed was the same as that for uranium. Thorium oxide was 
employed and the following results were obtained. Area of surface = 38 scp 
centims. ;— 
"Weiglit of 
thorium oxide. 
Current. 
gramme. 
•339 
• 0445 electrostatic unit per second. 
•66.5 
•0622 
vu*.-. ,, ,, ,, 
