3b.'2 EXPEDITION TO THE 



ble feature in the countiy, in order to ascertain what its 

 geological characters are, but as we were generally inform- 

 ed that no rocks are seen at its surface, that it presents an 

 uniformly smooth prairie-like appearance, the ascent be- 

 ing gradual and easy on both sides, and as it would have 

 taken three days to go to its summit and return, this ex- 

 cursion was not made. 



The Coteau des Prairies may truly be considered as the 

 dividing ridge between the tributaries of the Mississippi 

 and those of the Missouri. It is probably formed by the 

 elevation of the granitic or other primitive rocks, above 

 the usual level of the prairies. These may have been co- 

 vered in a mantle-formed manner by the secondary and 

 alluvial rocks, so as to be entirely concealed from view, 

 and to be made to assume the general features of prairie 

 land. We cannot, however, resist the belief, that a geolo- 

 gist who would follow it, in its whole course from the As- 

 siniboin to the Blue Earth, would be rewarded by the dis- 

 covery of the granitic formations, if not along the whole of 

 its crest, at least in some of the ravines which head near 

 it, and in which perhaps a superposition of secondary rocks 

 might be observed. 



After having left the Big Stone Lake, we crossed a 

 brook which retains the name of the St. Peter, but which 

 cannot be considered as part of that river ; the St. Peter 

 may, in fact, be said to commence in Big Stone Lake, and 

 this to be but a small tributary from the Coteau des Prairies; 

 it was less than seven yards wide. This stream soon leaves 

 the main valley and turns to the west, where a lateral 

 trench in the prairie, known by the name of a " Coulee," 

 gives it a passage. Had we visited the Coteau, we should 

 have ascended this Coulee, to trace the stream to its 

 source. It divides itself, as we are informed, into two 

 branches ; one of which runs in a direction west by south, 



