194 white: relations between coal and petroleum 



Organic remains of the spore or sapropelic type are found in 

 every bituminous shale or so-called oil rock that has yet been 

 examined. It is to the presence of such carbonaceous debris, 

 embracing sapropelic matter, all more or less disintegrated and 

 decomposed, that, in most cases, are due the dark tints of shales, 

 sandstones and limestones. The sufficiency of such matter to 

 produce the petroleum taken from the oil fields has been well 

 demonstrated. In this" connection, it will be recalled that, prior 

 to boring for underground oil in Pennsylvania, about 1848, oil 

 shales in several geological formations were distilled to obtain 

 the petroleum supplies of this country. Shales are now being 

 distilled for oil in Scotland and France. 



In this discussion, the terms oil rock and oil shale are applied 

 only to those rocks that yield petroleums when the organic 

 matter deposited in them as sediments is decomposed by destruc- 

 tive distillation. The terms do not apply to sandstones, porous 

 limestones, or other rocks, in which petroleum is merely occluded 

 or held in the interstices of the grains of mineral matter. 



To what extent the characters of the distillates obtained by 

 any given method from the different coals, cannels, bituminous 

 shales, and other oil rocks are due to differences in the composi- 

 tion of the original ingredient organic matter of the deposits is 

 not known. For my own part, I am inclined to attribute to 

 this factor certain differences in the characters of natural petro- 

 leums, such for example, as high sulphur or high nitrogen con- 

 tent, richness in asphalt or brownness, rather than any great 

 differences in the rank or grade of the oils. More probably 

 the principal differences in the actual rank of petroleums are. 

 in general, due to physical causes, as will later be indicated. 



TWO PROCESSES IN THE ALTERATION OF THE ORGANIC DETRITUS. 



The Biochemical Process 



In the foregoing summary we have considered only those 

 differences in the types of coal and other sedimentary organic 

 desposits that were determined at the initial stage, that is, at 

 the time of the deposition of the vegetal and animal debris. 

 These differences between the types of detrital hydrocarbon 



