236 Mr. Eve and Dr. Mcintosh on the Radium 



that the disintegration of radium is not affected by large 

 changes o£ temperature, and it is difficult to conceive of 

 the radium atom so closely surrounded by other atoms that 

 the a. particle would be prevented from escaping. 



3. Joly has suggested that radium may reach the earth 

 from external sources. At present there is little experi- 

 mental evidence in favour of this view, and it is not easy 

 to reconcile it with the fact that in radioactive minerals 

 uranium and radium exist in constant proportions. 



It must be remembered that in these investigations no 

 allowance has been made for the heating effects due to 

 radiothorium, uranium, and actinium. There is evidence that 

 radiothorium must be distributed in the earth, both widely 

 and in considerable quantity, for the active deposits of thorium 

 have been found in the atmosphere in most places where an 

 attempt to discover them has been made. This fact is the 

 more remarkable because the thorium emanation decays so 

 rapidly that only a minute proportion of it can escape from 

 the soil into the air. 



As the work of obtaining rocks in a state of solution is 

 somewhat lengthy, involving the expenditure of time and 

 materials, some experiments were made in order to ascertain 

 if the emanation could be driven off by simple heating. 

 Fifty grains of each specimen investigated were powdered 

 and passed through an 80-mesh sieve. The powder was 

 placed in a porcelain tube and heated for an hour in a com- 

 bustion-furnace. The air driven off by expansion was 

 collected over water, and at the end of the heating the air in 

 the tube was blown out, and all the gases thus obtained were 

 introduced into the electroscope and tested. The results 

 were compared with those obtained when portions of the same 

 specimens were in a state of solution,, and the emanation 

 driven off by boiling. The amounts found by heating ex- 

 pressed as percentages of the amounts found by boiling are 

 as follows : — 



Trenton Limestone 27 per cent. 



Tinguaite 49 „ 



Essexite 10 „ 



Nepheline Syenite . „ : 55 „ 



Leda Clay \ 47 „ 



Saxicava Sand 81 ,, 



It is, therefore, clear that the method does not give con- 

 sistent or accurate results. But when a large number of 



