ransome.] TOPOGRAPHY. 27 
thousand feet by volcanic accumulations in Tertiary times, and has 
been complicated by faulting and minor oscillations. No recognized 
trace of this surface remains. The topography, as we know it to-day „ 
is the product of stream erosion, modified by glaciation and the power- 
ful disintegrating action of frost at these high altitudes. It is essen- 
tial in all discussions relative to the lodes to keep in mind the fact 
that the entire topography is due to erosion, and that the highest 
peaks are but residuals which owe their relative height to the resistant 
materials of which they are composed, or to their distance from the 
main streams, but in no sense to direct and local elevations. 
With the exception of Bakers Park, Ironton Park, and perhaps the 
gently sloping bit of upland at the head of Henson Creek, commonly 
known as American Flats, no considerable areas of approximately 
level land occur within the quadrangle. The mountains rise in steep 
slopes, or in inaccessible dill's, often from 3,000 to 4,000 feet in height 
from the bottoms of the main canyons. The smaller streams descend 
these precipitous declivities in successions of waterfalls, or occupj^ 
small ravines or gulches of high gradient, such as Niagara Gulch near 
Eureka, Porcupine Gulch, or the gulches northwest of Howardsville. 
The larger tributaries have frequently excavated long canyons of 
moderate gradient, such as Cunningham and Poughkeepsie gulches,, 
but in these there is nearly always a point near the headwaters where 
a moderate gradient is succeeded by a much steeper one. Most of the 
streams, large and small, head in cirques, or "lasins" as they are 
locally termed, which often contain one or more lakelets. These 
basins form a very characteristic feature of the topography, and their 
general shape and character are admirably illustrated by the amphi- 
theaters just north of Sultan and Bear peaks (PI. V). 
The rock floors of these basins, often of somewhat hummock}^ char- 
acter, generally slope upward on three sides and pass beneath the 
talus or " slide rock," with which they are always partly filled. Above 
the talus and inclosing the basin on three sides are usually more or 
less precipitous cliffs, from which have fallen the fragments making up 
the talus at their base. As may be seen from the maps, these cliffs 
are merely the sides of narrow ridges, surmounted by peaks and inter- 
sected by cols or saddles which separate adjacent basins. The talus 
frequently extends up to a saddle, and it is then possible to pass from 
one basin to another over the divide. At their lower ends the basins 
are usually terminated by a precipitous descent to a gulch or to a 
second basin at the lower level. This relation is well shown in the 
case of Silver Lake Basin and Arrastra Gulch. When the connecting 
gulch is very short and steep, as Niagara Gulch, the basins have the 
form of hanging valleys. The talus that always lies against the cliffs 
and slopes rimming the basins represents in some cases the gradual 
accumulation of comparatively small fragments, such as may fre- 
quently be heard rattling down the cliffs during the spring and sum- 
