EXAMINATION OF WATERS OF GREAT SALT LAKE. 241 



Promontory and Oquirrh mountains, and Carriugton and Stansbury 

 islands, forming a similar chain farther west. At the present stage of 

 water Stansbury Island is connected with the shore, and Antelope 

 Island may be reached with little difficulty by fording. Mud Island, 

 usually known as Little Mountain, now rises from the mud flats north 

 of the Weber, but during the recent high- water stage it was an island 

 in fact. 



As is well known. Great Salt Lake is a relic of a great fresh- water or 

 brackish sea, Lake Bonneville, the history of which in geologic times 

 is written in the ancient beaches which terrace the mountain sides 

 which formed its shores. This lake had its fluctuations in level, rising 

 and falling probably in correlation to fluctuations in meteorological 

 conditions, but eventually its surface rose until it stood more than a 

 thousand feet above the present level of Great Salt Lake, when it 

 si)illed over the crest of an alluvial dam in Red Rock Pass and dis- 

 charged in a mighty river into the drainage system of the Columbia. 

 The erosive powers of this discharge over the loosely aggregated 

 alluvial matter soon cut a deep channel and the surface of the lake in 

 a short time fell nearly 400 feet, when further erosion was retarded by 

 the hard rock which was then reached, and the size of the effluent 

 stream thereafter was much diminished and became a factor of the 

 excess of precipitation over evaporation in the Bonneville hydrographic 

 basin, the lake level remaining approximately stationary. 



At a later period increasing aridity caused an excess of evaporation 

 over precipitation, the lake fell below the level of its outlet, and its 

 succeeding shrinkage in volume was due to a gradual process of desic- 

 cation. In its process of drying up the ancient Lake Bonneville was 

 divided into several portions, three of which, of considerable size, exist 

 as lakes of the present day. Of these, Great Salt Lake and Sevier Lake 

 are strongly saline, while Utah Lake, whose drainage basin receives 

 more water than is carried ofl'by evaporation, lias become fresh by the 

 continued discharge of its saline matter into Great Salt Lake via the 

 Jordan River. 



Historical knowledge of Great Salt Lake dates practically from the 

 time of the Mormon immigration into the valley, although it had been 

 visited previously by adventurous travelers and trappers. At the time 

 of the settlement of Salt Lake City, in 1847, the lake was at a lower level 

 til an it has since reached, and at the time of the first survey, in 1850, 

 its shores bore evidence that it had been at the existing stage for a 

 long time antecedent. Soon after, however, it began to rise, until in 

 1857 it stood nearly 4 feet above the level of 1850, its surface being at 

 about 6 feet on the Garfield gauge, established at a later period. By 

 1860 it had fallen again to its former stage, but in 1864 there began a 

 rapid swelling in volume which carried it to its maximum elevation 

 during historic times, in 1808, when it stood at a height of over 13 feet, 

 as referred to the zero of the Garfield gauge. From the high-water 

 stage then reached the lake has fallen in level, with periods of tempo- 



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