exdlich.] . SWEETWATER DISTRICT TOPOGRAPHY. 43 



lias removed enormous quantities of the rocks, and has left the surface 

 in the shape we now find it. Near the northern border of the region 

 under discussion we find remnants of large accumulations of sediment- 

 ary strata which have disappeared. Such remnants are expressed in 

 the form of prominent, isolated bluffs, and in a thickening of the strata. 

 In a certain sense, the gradual rise northward may be regarded as form- 

 ing a transition from the low country to the Sweetwater Hills. Geolog- 

 ically the two are in intimate connection, but their orographic relations 

 are not so evident. 



SWEETWATER HILLS. 



On many of the maps representing "Wyoming this small range is 

 designated as the u Sweetwater Mountains." Dr. Hayden has pointed out 

 in his report of 1870 that the appellation of "hills" was preferable. A 

 short distance south of Pacific Springs there are a few isolated bluffs — 

 table buttes — which may be regarded as the western terminus of the 

 Sweetwater Eange. From there eastward the hills present a uniform 

 appearance. Continuing without many breaks, they extend as far as 

 Saint Mary's. At that point the range is somewhat disrupted, owing to 

 a change in the geognostic structure. Steep granite hills, covered in 

 part by sedimentary strata of Carboniferous age are there found south 

 of the river. Valleys of erosion have cut in deeply, and narrow canons 

 indicate the changes of composition. From there eastward the range 

 of hills remains essentially unbroken, and continues to Elkhorn Gap. 

 Although the range retains a nearly even elevation of about 7,500 feet ; 

 it appears as a series of hills when seen from the valley north of it. 

 Creeks and streams have cut down deeply into the range, forming con- 

 venient low passes. At Elkhorn Gap we find a wide depression, breakin g 

 the connection of the hills. Near the western end of the gap there is a 

 prominent butte, comparatively isolated from the range. Seen from 

 a distance, where its base disappears, this butte shows itself as a hive- 

 shaped projection. East of the gap the range continues again unbroken 

 until it falls off steeply at Whiskey Gap. On the north side the hills are 

 regularly carved by erosion, while to the southward they present a more 

 even slope. Between Elkhorn and Whiskey Gaps the range is very 

 regular again. According to the nomenclature as applied to this region 

 the continuation of the hills eastward of Whiskey Gap is regarded as a 

 separate group. It has received the name of " Seminole Hills? Topo- 

 graphically and structurally, there is no reason why this distinction 

 should be made. The two groups belong to the same system in every 

 respect. They have undergone the same dynamical changes, are undoubt- 

 edly of the same age so far as elevation is concerned, and the only means of 

 separating them exists in the formation of the depression which breaks 

 the continuity. The relations of both groups to adjoining localities are 

 the same and they are of equal importance orographically. A short dis- 

 tance east of Sand Creek Pass our district ends, and the continuation of the 

 hills passes beyond it. While the southern slope of this range i s compara- 

 tively steeper than the northern one along the eastern half, the two are 

 nearly alike farther west. Starting from an elevation of about 0,500 feet, 

 a long-continued series of ridges slope gently down towards the Sweet- 

 water Eiver. In some instances, particularly near the western end of the 

 range, the angle of slope becomes steep, owing to the fact that the river 

 encroaches upon the hills. Near the little canon of the Sweetwater, about 

 west longitude 108° 20', the long flat-topped ridges begin. They are sepa- 

 rated from each other mostly by narrow dry gulches. In case they con- 

 tain water, they are usually wider and have flat meadows along the streams. 



