570 



Annals of the Carnegie Museum. 



Third. By taking the decrease in thickness of Division i between 

 Chazy and Valcour I.sland( 1 1.25 feet per mile) to compute the prob- 

 able southern extent of that division, it is found that it would have 



/ 5 3 





JA. 



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3^ 



Za 



4 



Fig. 3. Diagram to show the relations of the various sections. l,Aylmer, 

 Province (Quebec ; 2, Chazy, New York ; 3, Valcour Island, New York ; 4, Crown 

 Point, New York ; 5, Orwell, Vermont. In vertical scale I inch equals 225 feet. 

 The distance between the various sections is given, in miles, on the line at the base of 

 the figure. 



reached only 26.6 miles south from \'alcour Island. At the same rate 

 of decrease, the base of the Crown Point section is 461 feet higher 

 than the base of the Valcour Island section. It is not known that 

 this rate of decrease held, however, as there is no third point in the 



