112 MODERN SCIENCE READER 



similar to some crude mineral oils. Indeed, it seems highly 

 probable that when the coal has been formed under condi- 

 tions where no escape of gaseous matter could take place 

 owing to the impermeability of the low-lying strata, a 

 natural distillation at very low temperature has gone on 

 over long ages and some of the bituminous products of the 

 decomposition distilling into the earthy strata next to the 

 coal have formed with it the shales which differ from coal 

 in that the fixed residue left on their distillation consists 

 of earthy matter instead of coke. It is also perfectly well 

 known that in some of the more extensive peat bogs a 

 trickle of oil is occasionally found escaping from the de- 

 composing mass, showing that even in the early stages of 

 the action, oils are produced, while it was from a spring 

 of oil in the shale measures of the Alfreton Colliery that 

 Young first got the idea of utilizing shale for distillation 

 as a source of mineral oil. 



It has been known for centuries that in certain districts 

 of America and Eastern Europe a scum of oil would fre- 

 quently gather on the surface of the pools and streams, 

 and these districts have since become famous as the great 

 sources of American and Russian oil supply. Although 

 many observers cling to the belief that the oil fields have 

 been formed by animal or mineral agency, there seems but 

 little reason to doubt that our liquid fuels, like the solid, 

 are of vegetable origin, and are indeed by-products of great 

 subterranean distillations, in which at high pressures and 

 comparatively low temperatures the accumulated vegeta- 

 tion of past ages has been partly liquefied or even gasified, 

 as the same areas which yield our stores of mineral oil are 

 also famed for the production of natural gas. 



The Pennsylvania oil fields of America yield crude oil 

 consisting largely of members of that group of hydrocar- 

 bons which we know as the "saturated series," the lower 

 and more simple members of which are gases, and with the 

 fifth member commence to give highly volatile liquids 

 yielding the pentane which we use for our standard of 



