General McMahon — Further Remarks on Granite. 497 



Thus Palladium, which possesses this power in a higher degree than 

 any other metal, can absorb at a red-heat no less than 935 times its 

 volume of hydrogen.^ Doubtless hydrogen is not the only gas subject 

 to occlusion. The discoveries in our own time regarding Helium, 

 Argon, Uranium, and Eadium have also shown us that chemical 

 elements may long remain buried without their presenoe being 

 suspected, as in the case of Argon, the presence of which in 

 atmospheric air remained unsuspected until a few years ago. 



The case of the gas Helium is also highly suggestive. The rare 

 mineral Cleveite is the one with which Helium was at first associated, 

 but astronomers ^ affirm that it is rather abundant in the sun and 

 in many stars. The probability is, therefore, that it will hereafter 

 be found in connection with other terrestrial minerals. The chemists 

 of the future will no doubt discover buried in many rocks substances 

 of which the ordinary chemical analysis has up to the present time 

 taken little or no cognisance. 



With these ideas running in my mind, I find no difficulty in 

 believing that when beryl began to crystallise out of the magma 

 of the Satlej granite its molecules should have entangled and 

 brought down with them molecules of gas. The subsequent progress 

 of the mineral seems to have been as follows : — The molecules 

 came together above the critical temperature, bringing down entangled 

 with them two or more gases. As cooling progressed and the 

 tempei'ature fell, the molecules of gas and the molecules of water 

 in a gaseous state were enclosed in the mineral. 



As the temperature still further fell the water passed from its 

 gaseous condition to a fluid state, and as the rigidity of the beryl 

 increased, the enclosures of water and gas were more and more 

 compressed, until the dimensions of the cavities reached what we 

 now see them to be. As the water thus shut up gradually lost its 

 heat, the mineral matter, which had been held in solution by the heated 

 water, was deposited. That this progressive development actually 

 took place is, I think, proved by the evidence which shows that 

 the beryl began to crystallise when the granite magma was still 

 fluid, and that the beryl now contains inclusions of gas and of water 

 with deposited minerals. That the granitic magma, when in a fluid 

 condition, must have been above a red heat, is, I think, obvious. 



When I visited Vesuvius in the Spring of 1885 I descended into 

 the then existing crater, and approached its active centre as near 

 as was safe. I then saw with my own eyes that the lava on which 

 I stood was still red-hot immediately below its scoriaceous surface. 

 If lava, after it has been poured out on the surface of the earth, still 

 retains a red heat, we seem forced to the belief that an unconsolidated 

 granitic magma buried at plutonic depths in the bowels of the earth 

 must be in a still more heated condition. 



Mr. Hunt, in his September paper, dwells at some length on 

 volcanic conditions, and points to the case of Krakatoa as an 

 illustration of sea - water having gained access to the roots of 



1 Roscoe & Schorlemuer's Treatise on Chemistry, new edition, 1894, p. 137. 



2 Miss Gierke's " Problems in Astrophysics," 1903. 



DECADE IV. — VOL. X. — NO. XI. 32 



