1898.] PECKHAM — THE GENESIS OF BITUMENS. 117 



often lines cavities in the limestone in Herkimer county, New York, 

 and not only sometimes encloses crystals of quartz, but is often 

 enclosed in quartz crystals. These limestones are not crystalline. 



Above these formations just mentioned, in the Carboniferous 

 formation of both Europe and North America, anthracite occurs in 

 metamorphosed strata. In Wales, Belgium, the Alps and France, 

 such phenomena are frequent. The coal deposits of Massachusetts 

 and Rhode Island are enclosed in highly metamorphosed strata. 

 Much of the material is more nearly graphite than coal. Both the 

 coal and the enclosing strata are so distorted that the bedding is 

 destroyed and the material appears in segregated masses. 



In the trap dykes that have penetrated the sedimentary forma- 

 tions of the Connecticut valley and New Jersey, veins of carbona- 

 ceous matter occur. These dykes are intruded masses, no doubt 

 formed by the igneo-aqueous fusion of sediments that contained 

 organic remains. ^ 



TO. With the exception of the exudation of mineral pitch men- 

 tioned above, I have seen no notice that bitumen occurs in crystal- 

 line rocks, but always in rocks adjacent to or above them. There 

 are vast areas of the pal3eozoic formations of North America that 

 are not crystalline, that have been more or less subjected to the 

 action of steam and pressure at temperatures that have made them 

 more or less the subjects of metamorphic action. Some of these 

 rocks contain bitumen and others do not. The limestones in the 

 bluffs of the Mississippi river at Minneapolis and St. Paul contain 

 in the cavities of their fossils crystals of pyrite and rhomb spar. 

 They immediately overlie the St. Peter sandstone and are said to 

 belong to the Trenton group. Similar limestones in southern 

 Michigan contain bitumen, free sulphur and sulphates in large 

 amount. In southern Kentucky and Tennessee the limestones are 

 often coarsely crystalline and contain large encrinite stems that are 

 silicified. These same rocks contain geodes lined with crystals of 

 quartz. Other geodes contain sulphates of barium, strontium and 

 calcium, both with and without bitumen. In other localities the 

 rocks of this age are filled with bitumen widely disseminated in 

 small quantities. These rocks often exhibit very slight evidence of 

 the effects of heat, but frequently are found immediately above or 

 upon crystalline schists. " 



^ L. C. Beck, Am. your. Sci. (i), xlv, 335. I. C. Russell, ibid. (3), xvi, 112. 

 ^ S. F. Peckham, Reports of the Tenth Census of the United States, Vol. x, 

 ** Petroleum," p. 63. 



