PAPERS RELATING TO NATURAL HISTORY. 195 



numerous enough, belong to s.wamp or land plants, and no trace of petroleum 

 has been seen in these measures. But down from this red sandstone, the 

 Chemung is full of remains of Fucoides, and where they are found all the sand- 

 stone strata of this formation are more or less impregnated with oil. 



" Still lower the black shales of the Hamilton group are so much charged 

 with bitumen that they haye often been considered as the true source of the 

 DeTonian petroleum. There the remains are nearly, almost totally, obliterated. 

 A few teeth of fishes and small shells, rery rarely large trunks of Lepidodendroitf 

 nothing more, at least in those extensive deposits, generally of great thickness,, 

 which border our Western coal basins. The color of these shales, and the 

 bitumen which they contain, indicate a formation, under water, under the influ- 

 ence of a powerful vegetation ; and a marine vegetation, without doubt ; else, 

 besides the well-preserved trunks of Lepidodendron, which have probably been 

 brought floating, Ave should find there other remains of aerial plants. At 

 Worthington, in Ohio, where I have spent much time in searching for fossil 

 remains in these black shales, I have seen them often covered with round spoti 

 of coaly matter, varying in diameter from half an inch to one foot, showing no 

 trace of organism, and resembling some kind of round, hard Ulvaceae, like those 

 which are seen in great quantity attached to the muddy shores in shallow 

 water. 



" Descending further down in the Lower Devonian and Upper Silurian, we 

 see there also the rocks saturated with petroleum, and generally marked by an 

 abundance of Fucoidal remains. It is probably from the rocks of the Upper 

 Silurian that Prof. Brogniart obtained his Fucoides from Canada. In Ohio and 

 other Western States, where the Upper Silurian limestone is barren of remains, 

 it does not show any deposits of petroleum. In Canada the same rocks have 

 both Fucoides and fluid bitumen. Prof. Lesley, after an examination of the 

 east end of Canada, Gaspe, wrote me (5th January, 1866) : " All sorts of marine 

 vegetation of Upper Silurian and Devonian ages seem there in great abundance,, 

 and petroleum everywhere in the Devonian, and oozing from the lower Helder- 

 berg limestone formation. 



" Still deeper the Lower Silurian has small deposits of bitumen in cavities of 

 limestone, even when every trace of organism has disappeared. This fact agaia 

 is, I think, another indication of the relation of petroleum to a marine vegeta- 

 tion. For it is well understood that vegetable life has ruled the seas in its 

 minute representatives, Diatomaceae, Desmidiacese, long before animal life could 

 be supplied or sustained by it. These diminutive and primitive oil reservoira 

 are attributable to the concentration and decomposition of a local surplus of' 

 that primordial vegetation. 



" The geographical distribution of petroleum and that of the remains of 

 marine Alg8e present the same remarkable coincidence. At Oil Creek, Slippery 

 Rock Creek, in the Chemung of Virginia, Ohio, Kentucky, everywhere indeed 

 where oil has been seen, either in cavities or saturating the rocks, and where 

 the strata were open to view, a remarkable amount of Fucoidal remains hag 

 been observed. This cannot be a mere casual coincidence. 



" The discussion presented in the last part of this paper may then be closed 



Vol. XI. N 



