

hbakt.] VICINITY OF ST. PAUL AND MINNEAPOLIS. 315 



From Mendota to Fort Snelling the broad valley of the Minnesota is 

 crossed, and beyond the latter point the narrow gorge of the Mississippi 



is entered. At Fort Snelling one can easily see the difference between 

 the broad ancient gorge of the Minnesota and the Mississippi and that 

 ofthe Mississippi above this point.* The new narrow gorge is now 

 followed for a short distance, hut the railroad soon rises above it and 

 reaches Minnehaha falls after passing through a few shallow cuts in 

 the Trenton limestone. 



Minnehaha falls at present slmw a small volume of water ; this is due 

 to the damming np of the headwaters of the stream in order to raise 

 the level of lake Minnetonka. The height of the fall is 56 feet (17 m.) 

 from the brink to the surface of the water in the pool below the fall. 

 Below this the stream (lows eastward in a narrow gorge for about Too 

 feet (213 m.), when it enters a much wider gorge, and in this continues 

 to the river. This wider gorge is of interest as being an old channel 

 on one side of an ancient island in the Mississippi. The channel on the 

 other side was larger and cut back to the head of the island more 

 rapidly, thus tapping the supply of water for the smaller channel and 

 leaving a deserted gorge which ends abruptly in a steep bluff some dis- 

 tance above where Minnehaha creek enters it. 



In the vicinity of St. Paul and Minneapolis the Trenton formation con- 

 tains some soft green shales, which are very rich in well preserved 

 fossil remains; a few gasteropods, lamellibranchs, crinoids, and trilo- 

 bites are found; also a considerable number of brachiopods and large 

 quantities of bryozoans. In the Limestone itself remains of gigantic 

 Orthoceratites are often seen. 



* For a more detailed description of theso differences see the pa^es relating to the 



reccssiou of the Falls of tit. Anthony. 



