252 H. L. FAIRCHILD — GEOLOGY UNDER PLANETESIMAL HYPOTHESIS 



and a good degree of unity to the phenomena. Let us who have been 

 trained under the old hypothesis be on our guard in discussion of the 

 new theories that our arguments or objections are not derived from or 

 based on the old views. A new viewpoint is necessary to get the right 

 perspective of the problems. 



Source of the Hydrocarbons 



It has already been said that under the old hypothesis not only the 

 carbon dioxide now in the air but all the carbon stored in the stratified 

 rocks must have been in the primal atmosphere. The withdrawal of the 

 carbon from the air and the storing of it in limestone, coal, and petroleum 

 was formerly regarded as a divine process of purification, thereby fitting 

 the globe for habitation by man and at the same time providing him with 

 fuel. Geologists have long recognized in that view a serious difficulty, 

 for such immense quantities of carbon dioxide have been withdrawn from 

 the air since the advent of air-breathing animals that it is doubtful if its 

 full presence in the atmosphere at one time is consistent with aerial res- 

 piration. By far the larger part of the stored carbon is in post- Cambrian 

 strata, and a large portion in post- Paleozoic strata. The amount of car- 

 bon fixed in the stratified rocks has been variously estimated at from 

 20,000 to 200,000 times the present content of the atmosphere. The geo- 

 logic evidences as to climate and life in Paleozoic time are decidedly 

 unfavorable to the idea of a densely carbonated atmosphere. This point 

 will appear later in this paper. 



Another serious difficulty under the old hypothesis is the accounting 

 for the large deposits and localization of hydrocarbons and their asso- 

 ciation with volcanic phenomena. It seems probable that the carbon 

 dioxide of limestones is atmospheric or immediately oceanic. (There 

 may be doubt as to the organic origin of all limestones.) It seemed 

 plausible that the hydrocarbons of shales were also organic. From this 

 it was not along 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 limestones, 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, interro- 

 gations, and admissions of ignorance. A recent hypothesis holds that 

 the carbon dioxide of volcanic association is produced by the action of 

 meteoric water on imaginary metallic carbides in the earth's interior. 



The facts and phenomena relating to the occurrence of the hydrocar- 

 bons, which have no good explanation under the old hypothesis, are 



