192 white: relations between coal and petroleum 



a boghead or an oil rock; although if the rock is sufficiently low 

 in mineral sediments, it is in -reality a type of cannel. On the 

 other hand, if mineral sediments are mingled in quantities too 

 high to admit the classification of the rock as a coal, it is known 

 as an oil shale, or a bituminous shale. Lesser amounts of such 

 organic matter ordinarily gain recognition only as rendering 

 the shale ''carbonaceous." Deposits of decaying spore and pollen 

 material, with both vegetal and animal debris, laid down as 

 organic oozes, slimes or muds, were designated by Potonie as 

 ''sapropel."' 



Coals, including cannels, and oil shales from many regions 

 and geologic formations have been examined in detail under the 

 high-power microscope, and the organic detrital remains which 

 compose and characterize the several types have been splendidly, 

 sometimes even elaborately, demonstrated by paleontologists^ 

 both in Europe and America, though the botanical or zoologi- 

 cal classification of the fossil remains composing the deposits 

 may, in many cases, be subject to question. However, for our 

 present purpose, it is important only to note some of the qualities 

 or characteristics which certain among the different kinds of 

 organic debris impart to the deposits which contain them. 



The woody matter which forms the large part, at least, of the 

 ingredient substance of ordinary peats and their alteration prod- 

 ucts, xyloid coals, laminated coals, etc., is largely composed of 

 cellulose, lignose, xylose, etc., comprising carbohydrates rela- 

 tively high in oxygen. These ordinary coals, including those 

 commonly (though really inappropriately) called ''bituminous,'' 

 are therefore, as will be seen, characteristically high in oxygen. 

 They are, accordingly, characteristically rich in so-called humic 

 acid compounds. Hence, they have very properly been desig- 

 nated" as humic coals. On the other hand, the decay-resistant 

 elements, such as spore and pollen exines, seed envelopes and 



7 Potonie, H., Die Entstehung der Steinkohle, 5th Ed., p. 3. 1910. 



^Renault, B., Microorganismes des combustibles fossiles, 1893; Bertrand, C 

 Eg., Les charbons humiques et les charbons de pui-ins, 1898; Potoni6, H., Die 

 Entstehung der Steinkohle, 1910; Stopes, M. C, and Watson, D. M. S., Phil. 

 Trans. Roy. Soc. London, Ser.B., 200: 167. 1909; Thiessen, R., Bur. of Mines Bull. 

 38, 1913; Jeffrey, E. C, Economic Geology, 9: 730. 1914. 



3 Potonie, H., Die Entstehung der Steinkohle, p. 95. 1910. 



