474 DESCEIPTIVE GEOLOGY. 



the map, and flows north, through a gap in the limestone hills, out on to 

 the Desert. In the neighborhood of the settlement, which has an elevation 

 of 900 to 1,000 feet above the Great Desert, is considerable agricultural 

 land, which has been occupied by Mormon settlers. As the stream 

 approaches the Desert, its bed is cut deeper into the soft, muddy valley 

 deposits, and its waters become impregnated with the soluble alkaline salts 

 contained in the soil, which render it unfit to drink. In the spring and 

 early summer, its waters form a shallow lake on the edges of the Desert, 

 which, later in the season evaporating to dryness, leave considerable deposits 

 of alkaline salts. They form a thin, brittle crust, resting upon an exceed- 

 ingly fine clay soil, largely derived from the neighboring rhyolites and 

 Tertiary beds. A sample of this incrustation, mixed with some soil, yielded, 

 upon being submitted to chemical analysis by Mr. R. W. Woodward, the 

 following result : ' - 



Sodium. - 16.50 16.37 



Soda 26.47 26.39 



Potassa 2.55 2.51 



Sulphuric acid %;,--- 12.05 11.91 



Carbonic acid 18.27 18.36 



Chlorine.--.-- 23.20 23.14 



" Boracic acid undet. undet. 



99.04 98.68 

 with a theoretical combination of 



Sulphate of potassa 4.71 4.63 



Sulphate of soda 17.54 17.37 



Sesquicarbonate of soda 37.09 37.17 



Chloride of sodium 38.25 ' 38.14 



Excess of soda- 1.45 1.37 



The deposit would appear to consist of an admixture of sesquicar- 

 bonate of soda with a large percentage of alkaline sulphates, and common 

 salt, the usual impurities of the trona of commerce. The large amount of 

 potassic salt present is of considerable interest. The presence of boracic 



