74 



PROCEEDINGS OF THE CANADIAN INSTITUTE. 



The average elevation of the Highland Rim taken fi-oni the mean 

 leA'els for Railroad purposes gives on the 



feet. 

 Eastern and .south-eastern sides. . . . 1019 



ISTorthem side K 1 6 



Western and South-western sides. . 951 



R. R. Survey. 

 Mean of 13 Stations. 



" " 6 



or an average elevation of 942 for the whole Rim. The mean average 

 elevation of the floor of the Basin above the same point and from the 

 same authorities taken from twenty -nine stations is o<o7 feet. These 

 measiD-ements are above the level of mean tide in Mobile Bay. It 

 will thus be seen that the average amount of erosion necessary to 

 form this Basin would be a thickness of 375 feet extending over an 

 area of G190 squaie miles, and this after the surface of the country 

 had reached the le\el of the summit of the escarpment. Nor was 

 this the whole of the erosion that has evidently taken place in this 

 region of the world as there are many circumstances poiiiting to the 

 belief that denudation has removed an extent of sub-carboniferous and 

 carboniferous rocks if not greater, at least as extensive as the whole 

 of the Tennessee Coal field as at present existing. 



The aV)ruptnes3 with which the escarpment rises from the level of 

 the bottom of the Basin will be .seen from the following figures taken 

 from the aliiinments of the various Railroads crossinof it. 



T F0( >T OF 

 LOCALITV. ^^^^^ 



Tc.p OF 

 RiDOE. 



Differ- 

 ence. 



Di.st'nce 



Authority. 



Feet. 

 Near Edgelield .Junction. 563 



" Gallatin 694 



Feet. 

 895 



951 



1079 



1019 

 924 



841 



Feet. 

 332 



257 



265 



317 

 294 



317 



Miles. 

 1- 5 



1- 



5- 



6- 

 3- 



4- 



Survey. 

 L. N. R. R. 



" Tullahoma 1 e'4 



On Tennessee and Ala- 

 bama Railroad 702 



Near Pulaski 630 



Nashville, Chattanooga 



and St. Louis R. R. . . 524 



1 



R. R. Survey. 



C. S. R. R. 



i 

 1 



R. R. Survey. 



