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126 J. LeConte—Ancient Glacivrs of the Sierra Nevada. 
upon which is now in progress, will doubtless, in a great degree, 
do away with the eddies and under-currents prcduced by the 
sharp turn which the channel now takes at that point. It is 
not improbable that the successful removal of those obstructions 
will yet cause the sound entrance to be used in preference to the 
other by the fleets plying between European ports and the 
great commercial metropolis of America. 
lecturer desires to express his indebtedness to the discussions of 
Nore.—The lec 
tides and currents by Prof. A. D. Bache and H. Mitchell, published in the reports 
of the U. 8. Coast Survey. 
RT. XIX. —On some of the Ancient Glaciers of the Sierra 
Nevada ; by JosepH# LEConrxs, Professor of Geology. in the 
University of California. 
it filled the basin o e Tahoe, forming a great “mer de 
one of the outlets of the great “‘mer de glace” was by the 
Truckee River Cafion. The stage road to Lake Tahoe runs in 
this cafion for fifteen miles. In most parts of the cafion the 
rocks are voleanic and crumbling, and therefore ill adapted 
to retain glacial, marks; yet in some places where the rock 
is harder these marks are unmistakable. On my way to and 
from Lake Tahoe, I observed that the Truckee Cafion glacier 
was joined at the town of Truckee by a short but powerful 
_ * This Journal, III, v, 125. Proc, Acad. Sci. Oalif, rv (part 5), 259. 
