110 CHAMPLAIN DIVISION. 



New-York system. This view appears t" be supported by facts of another kind, and, if 

 any thing, of greater importance than those which belong (<> physical changes of surface* 

 III. fossils, for instance, belonging to this subordinate division as ii now stands, do not 

 .•mm in the succeeding rocks. Even where the Medina sandstone succeeds the-Graj sand- 

 stone of Oneida county, the fossils are not carried up. In fact, the entire fauna of the 

 Champlain rooks became extinct at the .lose of the period during which thej were depo- 

 sited. From these facts, then, this division must be regarded rather in the light of a 

 in. as w>' have just observed ; inasmuch as it is made up of a series whose characters 

 are peculiar, and which do not belong t" tin' preceding or succeeding era. It is true that 

 the fossils of the succeeding rocks do n.,i differ widely from those of the Champlain divi- 

 sion : many genera continue, though all do not; yet it is worthy of remark, that those 

 which disappear are quite limited in their ranges both vertically and horizontally. The 

 genera Ortkis, Atrypa, Strophomena, are continued ; but the crustaceans, as the Isotelus, 

 Menus, with some others, are not found after this period. 



§ 17. Recapitulation and summary of facts relating to the champlain division. 



1. The Champlain division is conformable to the succeeding divisions ; but as its members 



are placed upon the outside, and form a belt, consisting of a series of rocks adjacent 

 to the primary, they are more disturbed and broken than those of the succeeding 

 divisions. 



2. The inferior rock of this division, the Potsdam sandstone, is in the greatest force upon 



the western borders of Lake Champlain and the northern boundary of the State, 

 nearly encircling the primary nucleus of Northern New- York ; but in some places 

 it is absent on the south side of this nucleus, as in the Mohawk valley. In this 

 case, the next superior rock, the Calciferous sandstone, forms the base of the divi- 

 sion, and reposes upon the primary. 



3. The division embraces lithologically all forms of rocky strata : Conglomerates, breccia, 



sandstones, limestones, calcareous and sandy shales, and slate. Sandstones gene- 

 rally form the base (bin there are two locations where it is a conglomerate), and 

 the summit of the division : the former are red or brown ; the latter, gray. The 

 limestones occupy the inferior and middle portions of the series, and may be justly 

 described under one name in a general system. 



4. The principal depositories of metallic bodies are at the base of the system, where the 



peroxide of iron has been forced upward from the primary, and hence occasionally 

 occupies Bomeofthe inferior layers of the Potsdam sandstone. Galena and sulphu- 

 ret of iron form veins in the limestone, but they are not important. 



5. Agriculturally the most important masses are the limestones or calcareous shales, all of 



which decompose and form a rich and valuable soil. Water and frost greatly faci- 

 litate the proct — : ami masses of these shales, when thrown into heaps, speedily 

 break and crumble into a dark argillaceous earth. 



