44 [Assembly 



mens of both are in the cases, but it is not necessary to describe 

 particularly the peculiarities of each species. 



Above the Black-river limestone (or, where this is absent, 

 lying upon the Birdseye), we find one of the most interesting re- 

 positories of organic remains in the State ; a thick series of 

 limestones, usually black and fine-grained with thin seams of 

 slate toward the lower part, but grey and crystalline near the 

 top. They attain to an entire thickness of more than three 

 hundred feet, and, succeeding the lower rocks as already 

 described, their edges surround the great Adirondack region in 

 an almost unbroken circuit, traceable (in connection with the 

 lower limestones) on the State Greological Map by a belt of blue. 

 Seen along the Mohawk at Fort Plain and elsewhere, at Glen's 

 Falls on the Hudson, on the west shore of Lake Champlain, at 

 the Thousand Islands and Kingston on the St. Lawrence, they 

 also extend up the valley of the Black E,iver, and are crossed by 

 the West-Canada Creek at Trenton Falls, from which place they 

 take the name of the 



TRENTON LIMESTONE. 



In many places, they furnish building stone of excellent quality. 

 The State Lunatic Asylum at Utica, and the Cathedral of Mon- 

 treal, are built of the grey variety of this rock. 



The same series of limestone strata are seen at many points on 

 the Lower St. Lawrence, one of which is at the Falls of Mont- 

 morenci near Quebec. Westward, they may be traced near the 

 Bay of Quinte and onward by Lake Huron, Green Bay, and across 

 Wisconsin to the Mississippi. There they are increased by an 

 upper set of strata (not known at the east), called the Galena 

 LIMESTONE, from the large caverns and crevices of which the lead 

 ore of Iowa, Wisconsin and Illinois is obtained. Strata of the 

 same age with the Trenton limestone, probably a continuation of 

 them, are known west of Lake Winnipeg. Southwestward the 

 Trenton limestone and the succeeding Hudson-river group are 

 known in Tennessee, Missouri, and even Texas : they appear in 

 Kentucky and Ohio, covering the country round Cincinnati (where 

 they are known as the " Blue limestone ") ; and their edges 

 may be traced along the great Alleghany chain from Pennsyl- 

 vania southward to Alabama, in all which region, however, they 

 are much broken up and distorted in position, while their fossils 

 are less numerous and distinct than in New- York. 



