52 [Assembly 



is very conspicuous from its light color. Further east, the same 

 rock forms the falls of the Oswego river at Fulton ; but in the 

 Mohawk Valley it thins out, and becomes wanting. In South- 

 eastern New-York, however, it re-appears ; is very thick at the 

 Delaware water gap in New-Jersey and Pennsylvania, reaching, 

 in the latter State, the thickness of 1000 feet; and it maybe 

 recognized as far south as Alabama. 



The fossils of this rock are few, the most abundant and curious 

 are Fucoids, or Seaweeds, one of which, the Arthrophycus harlani^ 

 is known from the Niagara frontier to Virginia, and easily recog- 

 nized from its conspicuous and peculiar form (Fig. 13). There 

 are also a few small shells (Fig. 14). 



Above the Medina sandstone lies a series of sandstones, lime- 

 stones and shales, called the 



CLINTON GROUP, 



from one of the localities where they are well seen, the vicinity 

 of Clinton, Oneida county. This group of strata is hardly dis- 

 tinguishable east of Fulton county, appearing to thin out in tl^e 

 eastern part of the State, where it is all sandstone and greenish 

 shale. At the west, however, it contains two distinct layers of 

 limestone and two of greenish shale, which can be well examined 

 above the lower fall of the Genesee. Two thin strata of iron 

 ore are found in this group, and are extensively quarried in the 

 vicinity of Clinton : the ore is of a peculiar granular appearance 

 almost like small shot, and contains many fossils of small size. 



On the Niagara river, the upper limestone of this group is 

 about twenty feet thick, and a very solid, massive rock; project- 

 ing conspicuously from the eastern precipice somewhat more than 

 half way down from the top at the Suspension Bridge. At the 

 Falls, this layer is near the level of the water. 



This grqup of rocks extends westward through Canada, but 

 does not appear beyond Wisconsin as a distinct mass. As has 

 been said, it is not found in Eastern New- York, but re- appears in 

 Pennsylvania in enormously increased thickness, amounting to 

 nearly 2000 feet, and extends southward along the Appalachian 

 chain even to Eastern Tennessee. It seems everywhere to con- 

 tain beds of iron ore of the same character with those in New- 

 York, which are known m Pennsylvania as the Catawissa ore, 

 and ar^ worked for the Montour iron furnaces ; though in the far 



