GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 187 



ALKALI FEOM PUNTIA PASS.* 



The word alkali is used on the Plains to indicate a saline deposit 

 which covers often many miles of low, arid country, and appears in 

 streaks stretching far away in all directions and sometimes giving the 

 country the appearance of a plain covered by a sheet of snow. It is 

 very generally believed by the inhabitants that this alkali is the cause of 

 the sterility in connection with which it almost always occurs ; but the 

 fact is that one circumstance favors its continuance upon the soil and 

 interferes with vegetation, and that is the want of rain. Any continu- 

 ous rain would undoubtedly dissolve this material and carry it away in 

 the streams or through the subsoil. It is not quite certain that a soil 

 charged with the salts of which this alkali is composed would not fur- 

 nish more nutriment than another to certain kinds of growth. At all 

 events, where the experiment has been tried the plants have grown re- 

 markably well upon it with proper treatment. 



The probable origin of these deposits has been thought to be the 

 evaporation of numerous shallow pools, perhaps left by the subsidence 

 of a large inland sea or system of lakes, and the analogy in chemical 

 constitution between this material and the deposit around the margins 

 of still-existing pools (like the Soda Lake, twelve miles from Denver) 

 seems to bear out the hypothesis. . 



This alkali is a grayish- white deposit, mixed up with the dry roots 

 and stems of sage-brush and other vegetation, from which it derives 

 frequently a reddish-brown tinge. It is dry and efflorescent. 



It has a decided alkaline and salty taste and low specific gravity. 



It contains soda, lime, and magnesia, sulphuric acid, hydrochloric 

 acid, and a small quantity of nitric acid, and consists of sulphates of 

 soda, lime, and magnesia, chloride of sodium, and nitrate of soda. 



SODA FEOM SODA LAKE. 

 (12 miles from Denver, Colorado Territory.) 



A white, efflorescent salt, falling to powder on exposure to the air, con- 

 taining sulphate of soda, sulphate of lime, sulphate of magnesia, and 

 chloride of sodium. 



Per cent. 



Sulphate of soda 63.87 



Sulphate of lime 9.70 



Water of crystalization of the effloresence 21. 88 



Chloride of sodium, sulphate of magnesia., &c 4.55 



tl inclose the results of the analysis of the specimens of alkali col- 

 lected during last summer's survey of Wyoming Territory. 



No. 1. From Alkaline Lake two miles east of Independence Eock, in 

 the Sweetwater Valley : 



Per cent. 



Sulphate of soda, (NaO, S0 3 ) 73.17 



Chloride of sodium, (Na, CI) 3. 85 



Carbonate of soda, \ (by loss) 22.98 



100. 00 



* Prepared by Persifor Frazer, jr. 



t Prepared by Arther L. Ford, mineralogist to the survey. 



X Owing to this specimen's effervescing on being dissolved in water, it was impossi- 

 ble to determine the proportion of carbonic acid, but the salt seems to have been a 

 sesquicarbonate, the whole specimen being probably identical with or similar to that 

 referred to by Dana in his mineralogy, under the head of Trona, as occurring near the 

 Sweetwater River. 



