Extinct Glacier of the Salmon River Ravge. — Stone. 409" 
ciated and may have been brought in the lower part of the ice. A 
part shows few or no signs of glaciation, especiallj'^ the granite- 
boulders, and probabl}^ was brought here on the surface of the ice. 
These " nunatak moraines," as the}' may be named, show a marked 
contrast to the local rocks both in the glaciated shape of the stones 
and the materials of which the}' are composed. 
Another class of drift deposits on this area demands attention. 
A sheet of gravel and well rounded stones and boulders covers thfr 
bottoms of the main valle}' and of most of the lateral valley's until 
we approach the cirques in which the glaciers originated, where we 
find only unmodified morainal matter. Most of the stones have 
been very much rolled and rounded by water, but in places there 
is an admixture of stones bearing glacial scratches. The scratched 
stones become more numerous in the gravel as we go back from 
the main valley. This sheet of water-rounded matter has been 
eroded b}' the streams to depths varying from 30 to 70 feet, leav- 
ing the uneroded borders of the original sheet in the form of ter- 
races, known to the placer miners as the " high bars." In places 
they are only three or four hundred feet wide, but not far west of 
Leesburg one of these terrace plains expands to a width of nearly 
two miles. Excavations for placer mining show this gravel sheet 
to be from 10 to 60 feet thick, resting on the glaciated bed-rocks. 
The surface of the terraces has a slow ascent as we go back from 
the main creek, its rate being in most places about 100 feet per 
mile. A vast amount of well rounded gravel and cobbles continues 
along the lower part of this valle}'. 
It is evident that this water-rounded matter was rolled and pol- 
ished b}^ the subglacial streams. The surface is rather even, and 
we find no kame ridges nor reticulated kames. The gravel (in- 
cluding vast numbers of cobbles, boulderets, and boulders) was 
poured out in front of the retreating ice, being at the same time 
mixed with stones that fell down from the extremity of the ice and 
thus received too little water-wear to efface the glacial scratches. 
Possibl}' some of the broad tracts of the gravel and sand occup}' 
the place of glacial lakes caused by lateral glaciers continuing 
to flow across the main valley after the ice from the upper part of 
that valley had retreated. 
