60 THE GASES IN ROCKS. 



proportions on account of the reducing action of iron on carbon dioxide 

 and water-vapor. Meteorites of the stony type, unless absolutely fresh, 

 are more open to the suspicion of terrestrial hydration and carbonation. 

 But the Allegan meteorite gathered up, still hot, within five minutes of 

 its fall, has not been subjected to outdoor exposure, though it may have 

 absorbed a small amount of moisture and carbonic acid from the atmo- 

 sphere since being placed in the National Museum. It yielded somewhat 

 more than half of its own volume of gas. 1 Fresh material from the interior 

 of the Estacado, Texas, meteorite, heated in a vacuum in the presence of 

 phosphorus pentoxide for five hours at 150, and then allowed to remain 

 untouched for several days to enable the drying agent to take up the last 

 traces of moisture in the tubes, still yielded at red heat 0.86 volume of gas, 

 of which 36.25 per cent was hydrogen. 2 



These gases from stony meteorites resemble those from some igneous 

 rocks. That this correspondence should exist, is entirely in accordance 

 with the view that meteorites have been derived from the disruption of 

 small planetary bodies of the nature of the asteroids. As in the meteorites, 

 so in the rocks, that portion of the gases which can not have been produced 

 by chemical reactions at elevated temperatures, nor from the bursting 

 of rock-bound cavities, may fairly be assigned to occlusion. The computa- 

 tions indicating the excess of hydrogen obtained from quartz and beryl 3 

 over that which might have arisen from the interaction of iron and water 

 under the most generous assumptions show that, in some cases, more gas 

 may arise from a state of occlusion than from ordinary chemical action. 

 The amount of occluded gases may be actually greater than that indicated 

 by demonstrating the inadequacy of other modes of holding gas. But in 

 basic rocks containing hydrated minerals and an abundance of ferrous 

 salts, the resulting volumes of hydrogen must doubtless come largely from 

 the decomposition of the water of constitution, and the amount of occluded 

 gases, if any, is beyond determination by these methods. 



The gases argon and helium, which, according to current chemical 

 views, do not form compounds, must exist within rocks either mechanically 

 entrapped or in a state of occlusion. There are those, notably Ramsay 

 and Travers, who believe in the combining properties of argon and helium; 

 but the balance of opinion seems to be on the other side, so far as ordinary 

 terrestrial conditions are concerned. Lord Rayleigh concludes his paper 

 on the inactivity of these two gases, with this sentence: "There is, there- 

 fore, every reason to believe that the elements, helium and argon, are non- 

 valent, that is, are incapable of forming compounds." 4 



As the chemists' supply of helium comes from certain minerals, chiefly 

 those containing compounds of uranium, its occurrence in rocks is a well- 

 known fact. Recent studies have revealed the existence of helium in beryl. 5 

 Argon is perhaps more widely distributed than helium, Gautier having 

 detected this element in ordinary granite. The waters of many springs 



1 Analysis No. 106. 



2 Analysis No. 107. 



3 Ante, pp. 46-48. 



4 Lord Rayleigh, Proc. Roy. Soc., vol. 60, p. 56. 



5 R. J. Strutt, Nature, Feb. 21, 1907, p. 390. 



