212 Observations upon the Geology and Paleontology 



Silurian, and not more strongly than between the Hamil- 

 ton and Chemung." These remarks, together with giving 

 the geological position of Productus arcuatus by the same 

 author as "in limestone — below the Burlington lime- 

 stone — of the age of the Chemung group," are the only 

 intimations we have had that the fossils of the Chemung 

 rocks here were recognized above bed No. 6. 



SECTION OF ROCKS EXPOSED AT BURLINGTON. 



No. 1, arenaceous clay and fine-grained sandstone . . . . 25 to 80 feet 



Ko. 2, bluish gray limestone 6 inches 



No. 3, oolitic limestone 3 " 



No. 4, compact, fragmentary limestone 7 to 12 feet 



No. 5, fine-grained sandstone 4 to 7 " 



No. 6, oolitic limestone 2 to 4 " 



No. 7, brownish limestones and chert 40 to 50 " 



No. 8, grayish limestones 20 to 40 " 



The difference in the height of bed No. 1 above the 

 level of the river, is due to a gradual dip of all the beds 

 to the southward, and to very slight undulations ; the beds 

 of the whole series being quite conformable. The differ- 

 ence in the thickness of beds Nos. 7 and 8 is in a great 

 measure due to denuding forces in operation previous to 

 the deposit of the coal. 



Beds No. 2, 3, 5, and 6 are supposed to be of limited 

 extent; perhaps also bed No. 4, unless it should prove 

 identical with the lithograj)hic limestone of Missouri, 

 which it very much resembles. At a point on Honey 

 Creek, in Illinois, about ten miles from Burlington, the 

 Burlington limestone is observed resting upon a fine- 

 grained argillaceous sandstone of a visible thickness of 

 about twelve feet, which is evidently either No. 5 consid- 

 erably thickened, vvitii No. 6 wanting, or No. 1, with the 

 intervening beds to No. 7 wanting. 



No. 1 is generally of a light, greenish blue, weathering 

 to an ash gray, changing in color in different localities, 



