Moss—On the State in which Helium Exists in Pitehblende. 157 
The composition of the gas obtained by the decomposition of this pitchblende, 
neglecting sulphur dioxide and hydrogen, removed by the action of the hot copper 
oxide, is therefore 
In 100 Parts. 
CON e WG S.S86 93°35 
ORWAGH He as 112 “15 
Hen ware js ¥: 1-560 2-11 
Nw rice ai ag 3-239 4:39 
13°797 100-00 
An examination of the fused mass remaining from the decomposition of the 
pitchblende showed that the coarser parts of the powder had not been decomposed. 
The mass was treated with water, and the undecomposed pitchblende was separated 
by elutriation and found to weigh 10°3 grammes; this deducted from the 25 
grammes originally taken, leaves 14°7 grammes decomposed. ‘The undecomposed 
portion had probably lost part of its helium; but assuming this loss to be negligible, 
the yield of helium was 0106 c.c. per gramme of the pitchblende, and the yield 
of carbon dioxide was 4°686 ¢.c. per gramme. 
The total quantity of helium obtained both by grinding and by chemical 
decomposition was 0°107 c.c. per gramme, and of this total the yield by grinding 
alone constitutes 1:17 per cent. In the case of carbon dioxide the total yield by 
both methods was 4°686 ¢.c. per gramme, and only 0:0085 per cent. of this was 
obtained by grinding. From a specimen of calcite from the limestone in the 
neighbourhood of Dublin, I obtained by grinding m vacuo 0:024 c.c. of carbon 
dioxide, from each gramme of the mineral, along with sulphuretted hydrogen, 
hydrocarbons, nitrogen, and water. In this case there can be no question as to the 
gas being enclosed in cavities. Under a magnification of 200 diameters numerous 
cavities, some with liquid enclosures, can be detected. The heat resulting from 
the mechanical action of grinding, though it is inappreciable, might liberate some 
combined water; but the liberation of carbon dioxide and other gases can scarcely 
be attributed to any thermal effect. Now, the volume of combined carbon dioxide 
in 1 gramme of calcite is 222°4 ¢.c.; the enclosed carbon dioxide, liberated by 
grinding, is, therefore, 0°011 per cent. of the combined gas. In the specimen of 
pitchblende the corresponding proportion is 0°0085—a ratio of approximately the 
same order. ‘There is accordingly a very strong presumption, though no cavities 
can be detected in the pitchblende by microscopic examination, that they never- 
theless exist, and contain carbon dioxide, other gases, and water. It is difficult to 
resist the conclusion that the helium, which is liberated by grinding in much 
larger proportion relatively to the total quantity present, is also contained in 
