white: eelations between coal and petroleum 203 



Conforming to the prevailing usage in this country, I have, 

 in the following discussion, used the Baume system, in which 

 the increase in the number of degrees is inverse to the increase 

 in gravity. 



In most petroliferous regions of the world the oil pools lie 

 in or near (often beneath) formations carrying coals. Accord- 

 ingly, it is generally possible to learn the stage of the regional 

 metamorphism, approximately at least, by the extent of the 

 alteration of the coals where, as in most cases, analyses of the 

 carbonaceous shales in the oil-bearing strata are lacking. The 

 geographic relations of petroleum pools to the coal fields will 

 be at once seen if David T. Day's oil map of the United States, 

 recently pubhshed by the U. S. Geological Survey, be compared 

 with M. R. Campbell's coal map, pubhshed in Mineral Resources 

 for 1910. (See also Coal Resources of the World, Ottawa, 1914.) 



occurrences of higher rank oils in regions of greater 

 alteration of carbonaceous residues 



Is there any relation between the rank of the oils of any 

 region and the degree of the alteration of the carbonaceous 

 matter of the organic debris in the oil-bearing or in the overlying 

 formations? Do the petroleums show regional differences of 

 rank corresponding to or comparable with the differences in 

 the rank of the coals in the various provinces? Unsatisfactory 

 as the criteria employed in the comparisons may be, the answer 

 to these questions is not only affirmative but it is conclusively 

 so. A review of the data reported from the various oil fields 

 of the world leaves no room for doubt on this question. 



If we examine the oils of the United States, we find that 

 in those formations and regions in which the carbonaceous 

 detrital deposits (coals) are but little altered by dynamic influ- 

 ence, the oils are heavy and of low rank; that is, they are of 

 high gravity. On the other hand, in regions of more advanced 

 alteration of the residual organic debris, the oils are in general 

 of correspondingly higher ranks (lower gravities), the highest 

 degree of alteration of the residues being, in general, noted in 

 the regions of highest rank oil pools. 



