exdlich.] SWEETWATER DRAINAGE GLACIATION. 115 



the river. We observe in consequence, firstly, a widening of the imme- 

 diate river bottom, and, secondly, an accumulation of fine drift near 

 it. Wherever the Sweetwater passes through some narrow gap in the 

 lower half of its course, we generally notice a decided widening of the 

 bottom land immediately above the more restricted passage. This is 

 due to the accumulation of drift, which tended to equalize the level at such 

 points. At the localities where this occurs we will see that the river 

 follows a serj>entme course. 



ANCIENT GLACIERS. 



Between Elkkorn and Whiskey Gaps, on the northern slope of the hills, 

 the most striking remains of old glaciers were found. Directly east 

 of the first-named depression we find extensive deposits of drift about 

 half-way up the hills. They do not extend far down, however. A little 

 farther east, on a creek which we named Glacier Creek, there are exten- 

 sive moraines. Starting near the summit of the granitic hills, the glacier 

 moved down a narrow valley toward the north, receiving additional 

 masses of ice from branches on either side. Spreading in an .oval valley 

 between the outcropping sedimentary beds and the metamorphics, the 

 glacier covered an area of about two square miles. Finding its way 

 through a narrow gap, the ice moved down in the valley of Glacier 

 Creek, depositing very finely developed lateral moraines. These are 

 arranged in several parallel rows, showing that a number of small gla- 

 ciers must have passed down the valley. In height they amount to about 

 30 feet here. Lower down on the creek they become higher, until finally 

 a huge mass of bowlders and drift announces the termination of the 

 glacier. All the slopes and ridges of this immediate vicinity are cov- 

 ered with glacial drift. It is here usually distributed without any order 

 of arrangement, but in the valleys the moraines are well developed. 

 For a considerable distance eastward we find a continuation of the 

 same occurrences. So far as we could determine, the moraines do not 

 extend beyond the immediate base of the hills, but wide, grassy valleys 

 indicate the action of the waters formerly flowing- off from the glaciers. 

 These latter deposited a large amount of silt and soil, which now form 

 the meadow grounds. 



At the northeastern end of the Sweetwater Hills we find a large de- 

 posit of drift bowlders that has every appearanpe of morainal character. 

 It is placed along the upper granitic slope and on benches formed by 

 sedimentary strata. All the beds underlying this drift are entirely ob- 

 scured, a feature which is indicated in Section XIII. Metamorphic 

 bowlders mainly, and some composed of unchanged sedimentary material, 

 fona these moraines. It seems probable that the highest northern slope 

 of this portion of the Sweetwater Hills was at one time covered, to a 

 greater or less extent, by ice. Now it is densely timbered, and but few 

 outcrops of rocks in situ can be found. Wherever these are seen they 

 are smooth and rounded. From the higher elevation the ice moved 

 down along the northern slope, filling a number of narrow gulches and 

 finally collecting in a large field on Glacier Creek. 



DRIFT. 



From what has been said in previous pages, it is evident that a large 

 amount of drift must occur in the Sweetwater region. Besides the 

 Wyoming conglomerate and the glacial deposits, we find that class of 

 transported erratic material known as river drift. It occurs along the 

 river and is scattered in greater or less profusion over the adjacent bluffs. 

 Composed mainly of metamorphic material, a large portion of it has been 

 brought from the region directly at the end of the Wind Biver Mount- 



