732 D. WHITE LATE THEORIES REGARDING THE ORIGIN OF OIL 



of the various hydrocarbons would depend upon both the actual pressure and 

 the amount of uncondensed gas. Increase of temperature probably only acted 

 as an accelerator of the catalytic action." 



It may not be out of place to add at this point that most petroleum 

 theorists now assume that under certain circumstances, generally not 

 specified, filtration as proposed by David T. Day has operated, locally at 

 least, in changing the character of the crude oils while migrating. 



Influence of Ci-iemical Processes 



In a previous paper-^ I have shown that between coal, oil shales, and 

 petroleum there is much in common as to origin. Whether the ingre- 

 dient organic matter, be it plant or animal, will be in part transformed 

 to coal of the ordinary type, to cannel, to oil shale, to the organic residues 

 in so-called bituminous shales and carbonaceous shales, or to petroleum 

 and natural gas, is dependent upon the composition of the ingredient 

 organic debris, the conditions of its accumulation or deposition, and the 

 extent of the microbian action. ^^ Further, this question is determined 

 before the close of the initial or biochemical stage of the transformation 

 of the organic matter. On the other hand, the alteration of peat (bio- 

 cbemical stage) to coals of successive ranks, such as lignite, sub-bitumi- 

 iious, bituminous, etcetera, is, I hold, the result of geochemical processes 

 induced under dynamic influences, especially thrust pressures with their 

 attendant temperatures. The greatest changes attend the greatest and 

 most prolonged dynamo-thermal activity. This alteration of the organic 

 detritus is progressive, and is marked not only by physical changes in the 

 detrital deposit, but in particular by the gradual elimination of its vola- 

 tile matter, including volatile hydrocarl)ons ; and this takes place in the 

 cannels, oil shales, and bituminous shales, as well as in the coals asso- 

 ciated in the same formations or groups of formations and in the same 

 areas. Also it is found that up to the point of too great devolatilization 

 of the oil shales or cannels, the progressively more altered shales, when 

 distilled, yield the oils with the greatest amount of light hydrocarbons. 

 These distillates are, in effect, crude petroleums, though they do not exist 

 as such in the organic debris or residues which gradually become carbon- 

 ized as coal or as disseminated particles in shale, sandstone, etcetera. 



Noting the gradual elimination of the volatile hydrocarbons — the so- 

 called volatile matter — from the oil shale simultaneously with the devola- 

 tilization of the associated coals in the course of the progressive regional 

 alteration of the organic deposits, I have called attention to several other 



2'Moiir. Wash. Acad., vol. .", no. 6. 101,5, p. 189. 



^ White and Thiessen : Origin of coal. Bureau of Mines Bull. 38, 1913. 



