676 ‘The Great Salt Lake in Former Times. (November, | 
thickness of several hundred feet, and of these materials the 
terraces are formed. Near Salt Lake City, in digging a well, 
fresh-water shells were found in these deposits, forty feet below 
the surface; and on the north side of the lake, where these de- 
posits are very largely exhibited, the cuts in the railroad, through 
the gravel and sands, reveal the greatest abundance of fresh- 
water shells, showing that at this time the physical conditions 
were unusually favorable for the existence of fresh-water mollus- 
cous life. So far as I could ascertain, these conditions do not 
exist at the present time, or if they do, it must be only to a 
limited extent. From these observations I infer that a vast 
fresh-water lake once occupied all this immense basin ; that the 
smaller ranges of mountains were scattered over it as isolated 
islands, their summits projecting above the surface; that the 
waters have gradually and slowly passed away by evaporation, 
and the terraces are left to reveal certain oscillations of level and 
the steps of progress toward the present order of things ; and 
that the briny waters have concentrated in those lake basins, 
which have no outlet. The entire country seems to be full of 
salt springs, which have, in all probability, contributed a great 
share to the saline character of the waters.” 
Additional information concerning the geology of the lake has 
recently appeared in the report of Mr. G. K. Gilbert, of Wheeler's 
Survey of the Territories West of the One Hundredth Meridian. 
We shall attempt, with the aid of liberal extracts from this 
interesting report, to give some account of the ancient history 
of this great briny lake, which in past ages extended over such 
a large area and formed one of a series of vast inland lakes 
rivaling in size the present great lakes of the northern border 
of the United States. These ancient lakes lay in the depres- 
sions of the Great Basin, as it was called by F rémont, situated 
between the Rocky Mountains and the Sierra Nevada. 
The Great Salt Lake occupies the eastern portion of the Great 
Salt Lake Desert, which is divided from the Sevier Desert by a 
series of low ranges. These hills or insular buttes appear 
have been, as it were, submerged beneath a sea of detritus. “ If 
these hidden mountains rise as high above their bases as do their 
neighbors on the rim of the basin, we may, by comparing sum- 
mits with summits, learn something of the relative depression of 
the rocky bottom of the basin below its margin ; and it would 
appear, judged in this manner, to be not less than four thousand 
feet. And, on the same supposition, the desert sediments, which, 
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