On the Gases enclosed in Crystalline Rocks and Minerals. 453 



Kayser and Friedlander (' Chem. Zeitung,' vol. 9, p. 1529) have 

 stated that in a vacuum-tube fitted with platinum electrodes, and 

 containing atmospheric argon, the argon became absorbed by the 

 deposited platinum, and the tube then showed certain of the helium 

 lines. I have never been able to absorb argon to more than the very 

 slightest extent, and though I have often had argon-tubes, which have 

 become black, owing to the deposition of platinum, through which a 

 powerful discharge has passed for many hours, I have never noticed 

 any marked absorption. 



A specimen of argon, the lightest fraction obtained from Professor 

 Ramsay's diffusion experiments, was treated in the manner just 

 described. After several hours' circulation it was found that the gas 

 absorbed by the platinum consisted only of argon, and no trace of 

 helium could be detected. This process has also been applied to the 

 analysis of the gases from certain mineral springs ; the results of 

 these experiments form the subject of another paper. 



"On the Gases enclosed in Crystalline Rocks and Minerals." 

 By W. A. TILDEN, D.Sc., F.R.S. Received December 19, 

 1896, Read February 4, 1897. 



It has long been known* that many crystallised minerals contain gas 

 enclosed in cavities in which drops of liquid are also frequently 

 visible. The liquid often consists of water and aqueous solutions, 

 occasionally of hydrocarbons, and not unf requently of carbon dioxide, 

 the latter being recognisable by the peculiarities of its behaviour 

 under the application of heat. The liquid supposed to be carbon 

 dioxide has been found in some cases to pass from the liquid to the 

 gaseous state, and therefore to disappear, and to return from gas to 

 liquid at temperatures lower by two or three degrees than the critical 

 point of carbon dioxide. This seems to indicate the presence of some 

 incondensable gas, and as H. Davy found nitrogen in the fluid cavities 

 of quartz, it seemed probable that the alteration of the critical point 

 was due to that gas. 



My attention was drawn to this subject by the observation that 

 Peterhead granite, when heated in a vacuum, gives off several times 

 its volume of gas, consisting, to the extent of three-fourths of it 

 volume, of hydrogen (' Roy. Soc. Proc.,' vol. 59, p. 218). 



* The chief literature of this subject is contained in the following papers : 

 Brewster, < E. S. Edin. Trans.,' 1824, vol. 10, p. 1 ; ' Edin. J. Science,' vol. 6, 

 p. 115 ; Simmler, < Pogg. Ann.,' vol. 105, p. 460; Sorby and Butler, 'Koy. Soc. 

 Proe.,' vol. 17, p. 291 ; Yogelsang and Geissler, ' Pogg. Ann.,' vol. 137, pp. 56 and 

 257 : Hartley, ' C. S. Trans.,' 1876, vol. 1, p. 137, and vol. 2, p. 237, also 1877, vol. 1, 

 p. 241. 



