442 A. C. Peale—Ancient Outlet of Great Salt Lake. 
of both valleys (Cache, and Marsh Creek) the relation of the 
two must have been apparen 
The ‘gentle alluvial slopes” mentioned by Mr. Gilbert (on 
page 257) as being “divided for several miles by a steep-sided, 
flat-bottomed, trench-like passage a thousand feet broad, and 
descending northward from the divide” are white sandstones 
similar to those in the bottoms of Cache and other valleys of 
the Salt Lake Basin. The following elevations on the terraces 
in Marsh Creek Valley were obtained by barometrical observa- 
tions. 
Two miles — of Red Rock Pass on the east side of the 
valley, 5,187 fee 
ix miles = a Red Rock Pass on the edge of Marsh Val- 
ley, 5 pe - 
wenty-six miles ogee Red Rock Pass on the west side of 
the owen: ‘5, 117 fe 
The elevation of ie Bonneville beach is 5,185°7 feet + and 
it is evident that the Red Rock Gap (the walls of which do not 
exceed the elevation of 5,000 feet) could not have been a bar- 
rier to Lake Bonneville. The conclusion is therefore irresisti- 
ble that the result of Mr. Gilbert’s four or five years’ search is 
a mistake. 
In the third place Red Rock Pass was an outlet, but it was 
the outlet probably when the lake was at the level indicated by the 
rove Beach, When the barrier at the northern end of the 
Bonneville Lake was removed, that portion of the lake occupy- 
ing Marsh Creek Valley was completely drained, and Red Rock 
Gap became the barrier of the lake that remained. Then 
it was that the course of Marsh Creek began to be outlined, 
and the lowering of the lake was doubtless comparatively rapid 
until the level of the Provo Lake was reached. The line of 
the Provo Beach indicates a period of comparative permanence, 
but when the pass became lower than the lake, of course the 
lake was dramed. The elevation of the pass as obtained by 
rane level i ws 4,7 - feet, and the Provo Beach, according to 
65 feet below the Bonneville Beach,t 
which would an an eden of 4,820°7 feet for the former. 
In the fourth place I wish to call attention to two more of 
Mr. Gilbert's statements. On page 258 he says, ‘In Dr. Hay- 
den’s Preliminary Report of the field work of his survey for 
*I am indebted to Mr. Henry Gannett for all the elevations I use and for other 
sedosbie icdoraon har ‘while in the feld. 
t This slexatiots | is obtained athe adding 967-7 feet (the height of the one 
given r. Gilbert i se) 
on oe Ss mest of the ct oe vol. pg Ty 1218 fet, 
Union Pacifie Railroad. 
_} This Journal, vol. xv, April, 1878, p. 258. 
