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in respect to these conditions seems now quite well substantiated. 

 Our immediate district in late Cambric (Ozarkic) time sloped to the 

 east and received the thin deposit of Potsdam and Theresa beds laid 

 down in the western end of the St Lawrence trough. Uplift fol- 

 lowed throughout New York, producing unconformity between these 

 beds and those of the Beekmantown which follow. Beekmantown 

 subsidence seems to have commenced simultaneously on the east, 

 west and south sides of the Adirondacks, with a tilting of the 

 surface in our district here, so that its slope was to the south- 

 west, instead of to the east. This was quickly followed by tilt- 

 ing of the whole region to the east, stopping Beekmantown de- 

 posit on the west and south sides of the Adirondacks and confining 

 it to the eastern trough. From this trough a bay seems to have de- 

 veloped westward up the St Lawrence trough, during Beekmantown 

 time. The Beekmantown was brought to a close by another uplift 

 of the entire northern New York region. In the Theresa district 

 this time gap was a long one during which iooo feet or more of 

 Beekmantown rocks were deposited in the Champlain trough, and a 

 much greater thickness in other regions. 



Through these early times then our district had a general slope of 

 its surface toward the east, though with an intervening time of short 

 duration during which the slope was to the southwest. There were 

 three depressions, alternating with three elevations of the surface, 

 though apparently the deposits of the third depression just failed to 

 reach the district. 



In the Champlain valley the Beekmantown is succeeded by the 

 Chazy limestone formation, the two being separated by a slight un- 

 conformity, indicating that the Beekmantown was followed, as it had 

 been preceded, by general uplift of the whole area. Depression was 

 then renewed in that trough for the third time, and for the third 

 time a bay was developed westward from it. This Chazy bay, how- 

 ever, seems not to have reached as far westward as the preceding 

 Beekmantown bay, and certainly fell many miles short of reaching 

 our district here. 



The Champlain Chazy is divided into lower, middle and upper sub- 

 divisions. The typical Chazy rocks are limited to the Champlain 

 trough and its prolongation north and south. This trough was 

 separated from a much larger depressed area to the westward, by a 

 land barrier, which prevented the passage of organisms from the one 

 basin to the other. At the same time therefore in which the Chazy 

 rocks were being deposited in the Champlain trough, other deposits, 

 characterized by a different fauna, were forming to the west of them, 



