344 GLACIAL GRAVELS OF MAINE. 



and valleys we find the volcanic rock alone. The mountains rise to 

 heights varying from 11,000 to near 14,000 feet. They receive the first 

 onset of the Pacific winds, and the pi-ecipitation is great. The valley of 

 the North Fork was occupied by a glacier which left a terminal moraine 

 near Keystone, about 5 miles west from Telluride. Many of the slopes are 

 so steep that moraines would slide at once down to the bottoms of the 

 valleys, but in many places there is a sprinkling of erratics on the sides of 

 the valleys. Ophir and Trout Lake basins, on the South Fork of the San 

 Miguel, each contained glaciers which left moraines in the bottoms of their 

 valleys, but their gathering-grounds were small and they appear to have 

 been less than 8 miles in length. 



The bottoms of the valleys of the San Miguel River and its three 

 principal tributaries were once covered with a deep body of well-rounded 

 gravel and coarser matter up to bowlders. This original deposit has now 

 been eroded to depths of 30 to 70 feet, leaving portions of the old plain as 

 ten-aces on the steep sides of the canyons, the so-called high bars of the 

 placer miners. These terraces, growing finer by degrees, extend 40 miles- 

 irom the moinitains — how much more I do not know. They in part consist 

 of Tertiary drift. In these valleys the overwash apron of glacial gravel far 

 exceeded in bulk the moraines. The glacial gravel is found all the way 

 from the moraines up to the mountain basins. 



VALLEY OF THE UNCOMPAHGRE RIVER. 



This stream heads against Las Animas River and flows in the oppo- 

 site direction northward, and, having cut deep canyons through the Mount 

 Snefifies Range, emerges from the mountains a few miles below Ouray. 

 South of Ouray the very ancient quartzites are intensely glaciated, but 

 retain an uneven and hummocky surface. The gentler slopes of the moun- 

 tains carry sheets of drift which in composition and character resemble 

 those of the upper Las Animas Valley above described. Two V-shaped 

 valleys join at Ouray, below which point the valley is U-shaped and soon 

 broadens to a mile or more near Ridgway, where the Dallas branch joins 

 the main stream. Here a broad series of ridges and heaps of erratics 

 extends obliquely across the valleys of both branches just below their junc- 

 tion. Grlaciers came down both valleys and left these moraines, which are 

 more than a mile long and near half a mile wide, rising in places to 150 feet 



