60 Notes upon the Geology of the Western States. 



the Niagara is the most important limestone east of the Missis- 

 sippi river, both as regards the extent of sm'face occupied by it, 

 its thickness, and its mineral contents. 



It would be quite out of place at present to go into detail re- 

 garding the lead mines, and the zinc and copper ores, which equal- 

 ly belong to this rock, as I shall have occasion to speak of these 

 again in connexion with other facts relating to this subject. 



The shale of Rochester, Lockport, and Niagara Falls, accom- 

 panies the Niagara limestone every where as it does in New York, 

 but at the west it forms a very insignificant mass, generally not 

 more than twenty five or thirty feet thick, and bearing the char- 

 acter of the upper portions of the same shale in New York, be- 

 ing a harsh, sandy-like rock, crumbling on exposure to weather, 

 and almost destitute of fossils. 



The " Protean group,"* or the green shales, Pentamerus lime- 

 stone, and iron ores, are nearly or quite wanting, being only par- 

 tially seen in a few places in Ohio, and forming nothing worthy 

 of notice farther west, so far as my knowledge extends. The 

 peculiar fossil of this group, Pentamerus oblongus, or a species 

 so similar that I am unable to distinguish it, occurs in the Niag- 

 ara limestone in Iowa, and also in Ohio, as I am informed, not 

 having myself seen it in the latter place. Should such be the 

 fact, it proves the existence of this shell for a long period after 

 the destruction of the same in New York. 



In the state of New York the Protean group is underlaid by 

 the red shales and sandstones of Medina, the sandstone of Sal- 

 mon river, and the shales and sandstones of Pulaski. These 

 rocks occupy the basin of Lake Ontario, forming the southern, 

 eastern, and western, and more than half the northern boundary 

 of the lake, and may very appropriately all be merged in one 

 group, the Ontario. In Ohio, Indiana, Kentucky, and Illinois, 

 the red shale and sandstone, forming so thick a mass on the south- 

 ern shore of Lake Ontario, has entirely disappeared. Some small 

 portions of the Salmon river and Pulaski rocks are visible, but 

 the great mass filling the place of these is limestone in thin beds, 

 with alternating layers of green shale. In many places thin 

 wedgeform masses of gray sandstone are attached to the layers 

 of limestone, and here and there a distinct stratum may be seen, 

 with the same species of fucoides as characterize this group in 



The iron formation of western New York. 



