Hehshey.] 



The River Terraces of the Orleans Basin 



430 



Seven of these boulders were roughly measured and found 

 to have dimensions about as follows: 



1. 15x12x10 feet. 5. 18x10x18 feet. 



2. 15x10x10 feet. 6. 12x10x12 feet. 



3. 20x15x12 feet. • 7. 20x12x18 feet. 



4. 30x12x12 feet. 



There are somewhat smaller boulders of the same material, 

 but there is not a gradation from the largest to the smallest, so 

 that these boulders bear a relation to the ordinary gravel similar 

 to that between large glacial erratics and the finer rock fragments 

 of an ordinary till. They arc perfectly waterworn on all visible 

 sides. At first I was appalled by the problem which they seemed 

 to raise, but now I consider them the residua of a landslide. 



The present bank of the mine has a height varying between 

 sixty and ninety feet. Above the ordinary river deposit it 

 contains mostly local debris, which is distinctly stratified. Near 

 the upper end of the mine there is much angular debris of 

 serpentine and other local rocks from a neighboring gulch. The 

 upper twenty feet is a reddish brown clay, containing rock 

 fragments. This red clay stratum gradually thins downstream, 

 and only a few feet in thickness is left at the top of the bank 

 near the lower end of the mine. 



The following section in descending order was made nearly 

 midway of the bank, and is fairly typical of the deposit : 



SECTION IN MARKUSEN MINE. 



1. Reddish brown sandy clay, with angular rock 



debris 15 feet. 



2. Gray, finely stratified layers, mostly made up 



of angular and subangular slate debris. . . 40 feet. 



3. Reddish brown sandy silt, containing few rook 



fragments 10 feet. 



4. Ordinary river gravel 20 feet. 



Total 85 feet. 



No. 2 is a torrent fan of slate debris formed at the mouths of 

 several small ravines in the face of the steep slope back of the 

 mine. Its surface constitutes the present terrace remnant about 

 100 yards wide which rises at a considerable angle from the ed°e 

 of the bank to the foot of the steep mountain slope. During the 

 winter there are small creeks in the ravines, and they cross the 



