358 Origin of Carbonaceous Shales. 



may be examined with the discovery of iio other fossils than 

 seaweeds, which in some places quite cover the surfaces of the 

 layers. 



Economically, these shales are of great importance. In places 

 they attain a thickness of several hundred feet, have a wide geo- 

 graphical range, and with their percentage of carbon form a 

 store of combustible material, and a reservoir of power, far ex- 

 ceeding in quantity all the coal beds of the Carboniferous system; 

 they are also undoubtedly the source from which the great flows 

 of petroleum and carburetted hydrogen gas emanate at the 

 West. 



As we study the lateral extension and geological association 

 of these bituminous strata, we find evidence tliatthey have been 

 deposited in comparatively shallow and narrow seas, not far dis- 

 tant from the shores. 



Many suggestions have been made in regard to the origin of 

 the vast accumulation of carbonaceous matter contained in 

 these shales. 



In a paper on the Rock Oils of Ohio, published in the Report 

 of the State Board of Agricultnre for 1859, I attributed the 

 production of petroleum to the si3ontaneous distillation of the 

 organic matter present in these beds, and ascribed the accu- 

 mulation of this carbonaceoiis matter, for the most part, to 

 sea-weeds, but crediting animal tissues with a portion of the 

 product. Later, Mr. Lesquereux took the same view of the 

 origin of petroleum, and I think this is now endorsed by the 

 members of the Geological Corps of Pennsylvania who have 

 given the 2:)henomena of the production of petroleum the most 

 careful and prolonged attention. 



At the meeting of the American Association for the Advance- 

 ment of Science, held at Montreal in August last, a communi- 

 cation was made to the geological section by Prof. Edward 

 Orton, of Columbus, Ohio, in which, after citing many cases 

 where spheroidal flattened organic granules were found in the 

 Huron shale of Ohio, — bodies which he regarded as the spores of 

 sea-weeds, or lycopods, — he attributed the carbonaceous matter 

 which the shales contained chiefly to them. The paper of Prof. 

 Orton was subsequently published in the American Journal of 

 Science for September, 1882. 



