Nezv Hypothesis of Earth-Origin. — Fairchild, 105 
a densely carbonated atmosphere. This point will reappear 
later in this paper. 
Another serious difficulty under the old hypothesis is the 
accounting for the large deposits and localization of hydro- 
carbons, and their associations with volcanic phenomena. It 
seems probable that the carbon dioxide of limestones is atmo- 
spheric or immediately oceanic. (There may be doubt as to 
the organic origin of all limestones.) It seems plausible that 
the hydrocarbons of shales were also organic. From this it 
was not a long step (though a false one) to the assumption 
that all the masses of bituminous substances, under whatever 
conditions found, had been derived from the shales or lime- 
stones, and were primarily organic. The organic origin of all 
the hydrocarbons has been generally accepted in some vague 
way, but in the application of the theory many difficulties have 
been met, and the literature of the subject teems with doubts, 
interrogations and admissions of ignorance. A recent hy- 
pothesis holds that the carbon dioxide of volcanic association 
is produced by the action of meteoric water on imaginary me- 
tallic carbides in the earth's interior. 
The facts and phenomena relating to the occurrence of the 
hydrocarbons which have no good explanation under the old 
hypothesis are given a rational and consistent explanation 
under the new. Like the substance of air and ocean the ma- 
terials of the hydrocarbons are all primarily derived from the 
earth's interior, and the great localizations of bituminous mat- 
ter, specially in volcanic districts, are probably of immediate 
derivation from subterranean sources. A few of the facts 
which discredit the organic theory and confirm the volcanic 
theory may be marshalled as follows : 
1. The occurrence of great quantities of graphite in an- 
cient gneisses and in eruptive rocks. 
2. The occurrence of liquid carbon dioxide in the crystal- 
line rocks in notable quantities. 
3. The general occurrence in great abundance of hydrogen 
and hydrogen compounds in volcanic emanations ; the same 
being true of carbon dioxide. 
4. The frequent occurrence of mofettes or carbon dioxide 
springs, with constant flow, prevailingly in volcanic regions. 
Enormous quantities of this gas are exhaled in some localities. 
