esiiuch.] SOUTHERN AREA SAND DUNES. 137 



On the map which will appear .subsequent to this report the lake depos- 

 its are indicated, and it will be seen that the southern area of our dis- 

 trict was formerly much better supplied with water than it is to-day. So 

 far as could be determined from the general level and from the litholog- 

 ical character of the lake-beds, they were synchronously filled with water. 

 The persistence of some of them as lakes to the present time appears 

 to be due entirely to the composition of the deposits underlying - . Dry 

 beds were in close proximity to lakes of considerable size, and more than 

 once were they observed to show a lower level than the latter. In such 

 a case not mifrequently a more or less complete saturation of the sub- 

 soil coidd be noticed, which indicates that, first, it is in hydrological con- 

 nection with that of the lake close by, and, secondly, that the dry bed 

 is probably Hooded during the wet season. The latter fact is pointed out, 

 also, by the existence of alkaline deposits upon the surface. 



DRIFT. 



An abundant supply of drift covers the southern portion of our dis- 

 trict. Wherever it is composed of metamorphic and old sedimentary 

 material, Ave may regard it as redeposited Wyoming conglomerate. The 

 sandstones and shales prevailing in this region disintegrate readily and 

 form a species of finely comminuted drift which is spread over all the 

 bluffs and valleys. Coarse drift, in large masses, is necessarily of rare 

 occurrence. It is found, however, in the vicinity of all the older forma- 

 tions. 



From the character of the strata which supply the material for the 

 production of drift it is evident that a large quantity of it must partake 

 of the character of soil. The composition of this soil is a good one for 

 agricultural purposes, as will readily be seen if we consider the nature 

 of the beds furnishing it. Want of water, however, precludes the pos- 

 sibility of ever regarding this region as an agricultural one. Another' 

 portion of the drift is found in the form of sand, which forms extensive 

 moving deposits. 



SAND DUNES. 



In previous pages allusion has been made to the "sand belt" stretch- 

 ing diagonally across the southern portion of our district. It may be 

 stated as being 70 miles in length and from 5 to 10 miles in width. Be- 

 ginning in the west, near Packer's Creek, it follows a line north of east, 

 which brings it to the southern base of Mount Essex ; widening from 

 there on, it reaches Trail Lake ; passing on the south side of the lake it 

 extends to Death Lake ; thence it passes over the anticlinal upheaval, 

 disappearing near the summit, and continues from there to Sandy Creek 

 Pass, at the eastern termination of the Seminole Hills. On the eastern 

 side of Sweetwater and Wliiskey Gaps we find similar dunes, although 

 they are not so extensive. 



Composing these dunes we observe a fine white and light yellow sand. 

 It is almost pure quartz, containing but slight admixtures of feldspar. 

 From the disintegrating sandstones and arenaceous marls, which are so 

 prevalent in this southern area, atmospheric precipitation causes a re- 

 moval of the more easily transported particles. These are the cementing 

 clays. In this manner the sand is left entirely free, scattered over the 

 hills and bluffs and along the numerous slopes. Westerly winds exist 

 in this region during the greater portion of the year, and are mostly very 

 violent. By them the sand is picked up aud carried along in a line indi- 

 cating the greatest force of the wind. Wherever a gap occurs in a ridge 



