Since this observation, I find th at the presence of hydrogen in crystalline rocks has been recognised by other observers, notably by A. W. W right (‘ Amer. J. Sci.,’ Ser. 3, vol. 12, p. 171). In the course of a study of the gases from meteorites, W right obtained from a certain “ trap ” rock, the origin and character of which is not stated, at a low red-heat, “ about three-fourths of its volume of mixed gases, which were found to contain about 13 per cent, of carbon dioxide, the residue being chiefly hydrogen. Another specimen of trap containing small nodules of anorthite was examined at the request of Mr. Gr. W. Hawes, who had observed gas cavities in a thin section of the mineral prepared for microscopic examination. This gave off somewhat more than its own volume of gas, which was found to contain some 24 per cent, of carbon dioxide.”
Professor Dewar and Mr. Ansdell have also examined one or two rocks in the course of their researches on meteorites (‘ Roy. Inst. Proc.,* 1886). They found th at both gneiss and felspar, containing graphite, yield gas, which, upon analysis, was found to have the composition stated below. Occluded gas in volumes
of the rock. C02. CO. H 2. CH4. ]ST2. Gneiss............... 5-32 82-38 2-38 13-61 0*47 1-20 Felspar ........... P27 94-72 0‘81 2-21 061 P40
Dewar and Ansdell remark th at “ the small quantity of marsh gas, no doubt, comes from the disseminated graphite, but the presence of the hydrogen is more difficult to explain, and requires further investigation.”
I have lately been following up this question, and have obtained results which present some points of considerable interest. For materials I have been indebted chiefly to my colleague, Professor Judd, who has also supplied information as to the probable geological age of the specimens of rocks and minerals tested. All that I have examined yield permanent gas when heated in a vacuum. This gas varies in amount from a volume about equal to th at of the rock or mineral to about eighteen times that volume. I t usually consists of hydrogen in much larger proportion than that found by the observers just quoted, together with carbon dioxide and smaller quantities of carbon monoxide and hydrocarbons. Every specimen has been examined by the spectroscope for helium, but in no case could D3 be recognised, or any other line which would lead to a suspicion of the presence of this substance. The gas is very frequently, but not always, accompanied by water in notable quantities.
The gas is apparently wholly enclosed in cavities which are visiblein thin sections of the rock when viewed under the microscope, but as they are extremely minute, very little gas is lost when the rock is
