CHAMPLAIN DIVISION. 139 



The above estimate is offered as the maximum thickness of the rocks in New-York. It 

 must, hovel er) be taken in connection with the fact thai many of them are much thinner ; 

 and it" they occurred only with the thickness which they attain in a few localities, they 

 would not be regarded as distinct rocks, but as subordinate layers in other and more important 

 beds. Thus the Oneida conglomerate is about thirty feet thick in Oneida county ; but in 

 Ulster, it is between four and five hundred. The birdseye, which is always, however, a 

 thin rock, is only one or two feet thick at Tribe's hill ; while at Chazy, it is at least fifty 

 feet. The calciferous also varies greatly : several important and interesting beds are 

 wanting in the valley of the Mohawk, which exist in great force near Chazy. The Pots- 

 dam sandstone is wanting at Littlefalls, but is probably more than four hundred feet thick 

 in Mooers in Clinton county, and in fact all along the Provincial line. 



There are, therefore, two very curious features exhibited in the Champlain division : 

 the great irregularity in the thickness of the rocks composing it, and the suddenness with 

 which this change seems to have taken place. Still, in order to form an approximate idea 

 of the length of the era during which these rocks were being deposited, it is necessary to 

 ascertain the maximum thickness of the whole series. It is not probable, however, that 

 even the whole age of the Champlain division can be determined in New-York. If we 

 find individual members thicker and better developed in Pennsylvania, it is evident that 

 something must be added to the age of this division : the era, in other words, will be pro- 

 portionally lengthened. 



$ 16. The relation and connection of the champlain division with the succeeding 



rocks in the ascending order. 



The connection of the Champlain division with the rocks which succeed it in New- 

 York, is quite interesting as well as important. On the western and eastern sides of the 

 Hudson river, the upper members are succeeded immediately by the thin-bedded lime- 

 stone and shales of the hydraulic limestone of the Helderberg division. This is also the 

 fact at the northern terminus of the Helderberg range ; so also at Schoharie village, and 

 as far west as Cherryvalley. Near Utica, however, the upper rocks of which I am 

 speaking, or those of the Hudson-river group, are succeeded by the upper members of the 

 Ontario division, or the Clinton group ; while at Oswego, they are succeeded by the 

 Medina sandstone, the lowest member of this division. 



From these facts, it is inferred, that at the close of the period to which the Champlain 

 division belongs, the surface, or the rocks themselves, were subjected to oscillations, and 

 to movements which were more remarkable than those which occurred during the period 

 of their deposition. It must be admitted, however, that the intervals between these move- 

 ments were rather wide, inasmuch as rocks of considerable thickness were sometimes de- 

 posited between them. These facts, however, indicate that the close of this period was 

 one of considerable consequence ; and that we should probably be justified in considering 

 the Champlain division rather as a system by itself, than as a subordinate division of the 



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