VALLEY OF SALMOjS^ EIVEE. 351 



angular than ordinary bowlders of decomposition. The proportion of 

 glacial gravel to morainal matter is smaller than in any other glaciers of 

 the same size that I have found in Colorado. 



In the higher cirques of this region there are numerous fields of per- 

 petual snow. One of these in a valley lying on the northeast slopes of 

 Hague's Peak is consolidated to ice and exhibits transverse crevasses. It is 

 plainly sliding, if not flowing, down the mountain side. It appears so 

 much like a true glacier that I have named it the Hallett glacier, after the 

 discoverer. 



VALLEY OF THE SALMON RIVER, IDAHO. 



Many local glaciers originated in the Bitterroot Mountains and flowed 

 down into the valleys of the Salmon River and its tributaries. The Lemhi 

 Valley for man}^ miles above Salmon City is several miles wide. It is a 

 valle}^ of erosion in sedimentarj^ fresh-water lake beds. In the bottom of 

 the valley is an extensive plain of rounded gravel and cobbles, while on the 

 tops of mesas 200 to 300 feet higher is a thin sheet of similar material. 

 This higher gravel may be due to a more ancient glaciation than the last, 

 or it may have been formed on the margin of a great confluent glacier that 

 filled the whole valley. It is probable that some or all of these are beach 

 pebbles of the old lake. 



West of Salmon City lies the Salmon River Range of mountains. 

 They rise rather steeply from the valleys of Salmon River and its trib- 

 utaries up to an altitude of 6,000 to 9,000 feet. The main range lies nearly 

 north and south, and there are several spurs reaching out to the west and 

 northwest. The rocks are very ancient quartzites, slates, and schists with 

 intervening and bordering- areas of coarser granites and a few extrusions of 

 rather recent acidic volcanic rocks. The original masses of upheaval have 

 been dissected into many valleys and basins, and show plainly the marks 

 of geological old age. The mountains are well exposed to moist winds 

 from the Pacific Ocean, and the precipitation is large. 



Napius Creek drains a large area on the western slopes of these 

 mountains and flows into Big Creek, itself a tributary of Salmon River. I 

 have had opportunity to partially explore the upper 20 miles of this valley, 

 extending 7 miles west from the old mining camp of Leesburg to the 

 so-called Falls of Napius Creek. Here the stream cuts through a high 

 ridge of granite, and thence descends by a series of rapids and cascades to 



