310 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



that they were nit by the recession of the Falls in the same manner as 

 the POCk beds, and they do not conform in their undulations to the out- 

 line of the rock as if the gorge were present when they were formed, 

 as in St. Paul. There is no spreading of loam over these cat edges, 

 except what has fallen down from above at the time of their removal 

 or subsequent to it. At Fort Snelling the direction of the Mississippi 

 changes abruptly at a light angle, and the river enters the wider gorge 

 in which the Minnesota Hows, which gorge is entirely out of proportion 

 with the amount of wafer that it carries. This gorge (of the Minne- 

 sota) continues in the same iirection and with the same width beyond 

 the confluence with the Mississippi, but takes the name of the latter 

 stream; one mile below Fort Snelling this gorge is a mile and a half 

 wide (2*4 km.). 



These features of greater age, pertaining to the bluflsof the Mississippi 

 below Fort Snelling, are seen in the old rock bluffs of the river above 

 the mouth of Bassetts creek as far as Shingle creek. The rock there 

 is deeply changed in color and is bid by the drift, and the bluffs, as left 

 by the more ancient river, are far apart, the old gorge being three or 

 four times as large as that between the Falls and Fort Snelling. These 

 rock bluffs, consisting of the same limestone as that which at the Falls 

 is below the water, here rise from 30 to 40 feet (9 to 12 in.) above the 

 river and are buried under loam or drift and loam. This pari of the 

 old valley continues southwardly at tirst by way of Basse! ts creek, 

 across the western suburbs of Minneapolis, through the valleys occu- 

 pied by lakes Calhoun and Harriet, and joins the Minnesota at some 

 point above Fort Snelling, the precise locality being hid by a deposit of 

 drift. It was cut down into the St. Peter sandstone over 100 feet (30 in.) 

 at least, as shown by the well at the Sumner school house, and about 

 27o feet (84 m.), as shown by the deep well at the Lakewood cemetery. 

 This would show that probably the ancient valley of the Minnesota, 

 where it passes Fort Snelling. and all the way through Ramsey County 

 and below, has been tilled more than 200 feet (Gl m.) by drift that origi- 

 nated since the excavation of the gorge. This supposition is borne out 

 by all boriugs that have been made between the rock bluffs at lower 

 points, as at West St. Paul and at Lake City on Lake Pepin. Such 

 excavation is not found in the river gorge between Fort Snelling and 

 the Falls of St. Anthony, the solid rock being found not more than 25 

 feet (7*8 m.) below the bottom of the water. 



These facts warrant the conclusion that that part of the Mississippi 

 gorge above Fort Snelling has been excavated by the recession of the 

 Falls since the last general drift movement, and that prior to that event 

 there was a gorge which passed from the present channel of the Missis- 

 sippi, at the mouth of Lassetts creek, southward to the great gorge of 



