556 THE FRESH- WATER LOCHS OF SCOTLAND 
water-sheets, a few inches deep, in the wet season, where smooth plains 
of barren sun-baked mud, or " playas,"" remain in the dry months. 
The old shore-lines, marked by cliffs, bars, and deltas in the Great 
Salt Lake region of Utah and in north-western Nevada, indicate a 
past humid climate, and show that formerly these basins held large 
lakes that rose nearly a thousand feet on the adjoining mountain flanks. 
Lake Bonne- The Great Salt Lake of Utah is a relic of the much larger lake 
which has been given the name of Lake Bonneville. In superficial 
area Lake Bonneville was probably nearly equal to I^ake Huron, and 
had a maximum depth of 1000 feet. Of this pristine lake the 
western limit may still be regarded as undefined, though the principal 
divisions were probably as follows : — 
(1) The main body, covering the area of the existing Salt Lake 
and its shores eastwards to the Wasatch Mountains, and 
westwards to beyond the 114th meridian. 
(2) Cache Bay, covering the present Cache Valley in Utah and 
Idaho. 
(3) Utah Bay, occupying the valley of the present Utah Lake in 
the east-central part. 
(4) Sevier Bay, and (5) Escalante Bay, both to the south. 
The topographical elevations of the Bonneville area, once existing 
as islands and archipelagoes, now appear as hills and mountain spurs, 
with valley passes in place of the old-time straits. On the Great 
Desert the hills are half buried in lacustrine sediments, and rise 
from the lake-floor as sharply as do the present islands from the 
water-level of the Salt I^ake. 
As the waters of Lake Bonneville fell, the lake was divided into 
separate bodies, and the after-history of each lakelet was determined 
by its own conditions of local supply and evaporation. In many of 
the lakelets evaporation has resulted in complete desiccation, and in 
the deposition of rock-salt, usually associated with gypsum. The 
gypsum IS occasionallv found as small free crystals, which on the 
Sevier Desert are drifted by wind action into great glistening dunes. 
Professor Russell estimates that the dunes in one locality contain 
about 450,000 tons.^ 
Most of the Bonneville lakes are alkaline, or salt, though a few 
fresh-water bodies of small dimensions do occur, including : — 
Utah Lake, 27 miles long, IS miles broad, having an area of 
127 square miles. The overflow from this lake is conveyed 
by the Jordan River to the Great Salt Lake in Utah ; 
hence it is fresh. 
Bear Lake, discharging through Bear River into Great Salt Lake. 
Among the salt and alkaline lakes of the Great Basin are : — 
1 Tahiiage, "Lake Bonneville," Scott. Geogr. Mag., vol. xviii. p. 471, 1902. 
