AMERICAN JOURNAL OF SCIENCE. 
[THIRD SERIES] 
Arr. XLII.—The Outlet of Lake Bonneville ; by G. K. GILBERT. 
Some of the readers of the Journal will remember that the 
name “ Lake Bonneville” has been applied to a great body of 
water which formerly covered the desert basins of Utah. Its 
Most Conspicuous vestiges are its shore lines, and from them it is 
known that the ancient water surface was more than ten times 
as great as that of Great Salt Lake, and the ancient water level 
was about one thousand feet above the modern. 
Tt was early surmised that the ancient lake was freshened by 
overflow, but the point of discharge was for a long time undis- 
Covered, and it may be said to be still in controversy. The 
present paper takes up the subject of the outlet where it was 
left nearly two years ago. 
In this Journal for April, 1878, the writer maintained that 
the point of outflow was Red Rock Pass, Idaho, at the north 
end of Cache Valley; that the discharging stream descended 
through Marsh Valley and thence continuously to the Pacific 
Ocean ; and that, flowing over soft material at first, it gradually 
€xcavated at the Pass a channel more than three hundred feet 
deep, and lowered the lake level by the same amount. In the 
June number of the Journal, Dr. A. C. Peale controverted m 
Conclusion, declaring, first, that the original altitude of Red Rock 
28s was considerably below the highest level of Lake Bonne- 
ville ; second, that the ancient show ine exists in Marsh Valley 
at the north of the pass, just as in Cache Valley at the south; 
and finally, that the real point of discharge, when. the water 
Stood at the Bonneville level, was about forty-five miles north 
of Red Rock Pass, 
Am. Jour, oneiscateer “ame VoL. XTX, No. 113,—May, 1880, 
