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256 G. K. Gilbert—Ancient Outlet of Great Salt Lake. 
Art. XXXVI.—The Ancient Outlet of Great Salt Lake; a 
letter to the Editors, by G. K. GILBERT. 
Great Salt Lake has no outlet, and its fluctuating level is 
determined by the balance between inflowing streams and 
solar evaporation. On the surrounding mountains there are 
water-lines rising in steps to a thousand feet above its sur- 
face, and showing that in ancient times a great body of water 
occupied its basin. This ancient body, known as Lake Bonne- 
finding it in Idaho, at the north end of Cache Valley, the locality 
being known as Red Rock Pass. The circumstances were suc 
as to leave no doubt in my mind that I had determined the 
actual point of outflow, and on my return to the East I made 
the announcement without reservation in a communication to 
ell has charge. t, in 3 
January, 1878 (p. 65), there sa a statement (apparently on 
Dr. F. V. Hayden, but without signature) 
. 
: season, h 
etfs ancient outlet of the great lake that once filled 
ence and position of the ancient outlet beyond question. 
If Lake Erie were to dry away, and a Beologat of the future 
should examine its basin, he would easily trace the former shore- 
line around it. At two points he would find this line interrupted. 
At Detroit and at Buffalo he would meet with narrow, trough- 
