548 



slopes in the plain *. No chain exists be- 

 tween the sources of the Missouri and the 

 Assiniboni, which is a branch of the Red River 

 and of Hudson's Bay. The surface of these 

 plains, almost all in savannahs, between the 

 polar sea and the gulph of Mexico, is more 

 than 270,000 square marine leagues, nearly 

 equal to the area of all Europe. On the 

 north of the parallel of 42°, the general slope 

 of the land runs towards the east; on the 

 south of the parallel, it inclines towards the 

 south. To form a precise idea how little 

 abrupt are these slopes we must recollect 

 that the level of Lake Superior is 100 toises ; 

 that of Lake Erie, 88 t. ; and that of Lake 

 Ontario, 36 t. above the level of the waters 

 of the Ocean. The plains around Cincin- 

 nati (lat. 39° 6'), are scarcely, according to 

 Mr. Drake, 80 t. of absolute height. To- 



* See above, Vol. iv, p. 151. 

 t Tanner , American Atlas, 1823, p. 9. Amos Eaton and 

 Stephen van Rensselaer, Geolog. Survey of Erie Canal, 1824., 

 p. 151. In the United States, the slope of the Missouri is 

 estimated from its confluence with the river Platte (lat. 41° 

 3' 13") as far as its mouth in the Mississipi, (lat. 38° 51' 39", 

 long. 92° 22' 55'') from 3 to 4 miles an hour, or 14 J 

 inches of French feet by the English mile of 827 toises ; the 

 slope of the Mississipi, from its confluence with the Missouri 

 to the sea, is estimated at 10* inches. (Long, Exped. Vol. ii, 

 Append, p. xxvi, xxviii j and above, Per. Nar. Vol. iv, p. 

 240.) 



