CHAMPLAIN DIVISION. 
139 
The above estimate is offered as the maximum thickness of the rocks in New-York. It 
must, however, be taken in connection with the fact that many of them are much thinner ; 
and if 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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