white: relations between coal and petroleum 193 



certain cuticles, are generally provided with resinous, waxy or 

 oily protective substances. These, as well as the resin grains 

 with which they are in most cases mingled, are all character- 

 istically very high in hydrogen and low in oxygen. Thus it 

 happens that the rocks in which they are prominent are from 

 the start, as initial organic muds, more distinctly bituminous in 

 composition. As the fossil remains last named, mingled with 

 other fat-, oil- and albmninoid-produdng animal and plant 

 ingredients, predominate more and more, the contrast with the 

 ordinary — the humic — ^coals, becomes still stronger, the most 

 marked contrast being found in the so-called algal deposits, 

 which characterize many of the typical "oil shales.'^ Further, 

 as the high-hydrogen ingredients become prominent or predomi- 

 nate the fuel in general becomes richer in volatile matter and 

 higher in calorific value. Finally, it is to be noted: First, that 

 these deposits compose or characterize the oil rock series, as 

 has been pointed out by Renault, Bertrand, Potonie and others; 

 and second, that in succession the cannels, boghead cannels, 

 cannel bogheads and bogheads appear to yield, on artificial dis- 

 tillation, larger proportions of petroleum. A Reinschia boghead, 

 the so-called kerosene shale of New South Wales, is said to run 

 as high as 87 per cent in volatile hydrocarbons. 



Deposits containing in large proportions such organic detritus, 

 characteristically high in hydrogen and low in oxygen, are typi- 

 cal mother rocks of petroleum. As the proportions of waxes, 

 exines and resins become greater in the deposit, the distillates, 

 obtained by the artificial distillation of the fuel, approach in 

 characters more nearly to the natural petroleums; and when they 

 constitute the greater part of the organic detritus, as in the 

 cannels, or .when, finally, the material is more distinctly ''sapro- 

 pelic," containing great numbers of, or even composed almost 

 wholly of the so-called algae, the artificial distillates are, in gen- 

 eral, not only much greater in volume, as is to be expected on 

 account of the composition of the original debris, but they form 

 petroleums of higher ranks. It would appear that, other things 

 being equal, the maximum yield of oils of high quality is obtained 

 from the supposed alga coals or bogheads. 



