XVill INTRODUCTION. 
to the underlying geological structure of the region. The valleys are 
generally narrower and deeper, the mountains more rugged and precip- 
itous, and the surface of both is more luxuriantly covered with forest and 
plant growth. 
The most striking and characteristic feature of the scenery at Aspen 
is the narrow spur or ridge to the west of the town, lying between the 
valleys of the Roaring Fork and Castle Creek, which is generally known 
as Aspen Mountain. The northern portion of the spur to which this 
name is applied rises from the valley flat on which the town is situated in 
a slope whose steepness is exceeded only by that of the western slope of 
the same spur toward Castle Creek. How steep either slope must be will 
appear when one considers that the base of the mountain is only from a 
mile to a mile and a half wide, while its crest is 2,000 to 3,000 feet above 
the valleys that lie at the base on either side. As seen from the town, this 
ridge appears to have three summits, to which the names Aspen, West 
Aspen, and East Aspen mountains have been given, the first being the 
main crest of the spur, West Aspen Mountain its rugged northern point, 
and Kast Aspen Mountain the more rounded portion of the spur, stretching 
northeastward at the gateway of the Roaring Fork Valley, where the river 
issues from the granite region of the Sawatch. 
East of the town, between Roaring Fork and Hunter Creek, rises the 
steep but rounded spur called Smuggler Mountain, named from the mine 
that was early opened upon it, while northward, forming the eastern wall 
of the lower part of the valley, is the long, flat-topped spur called Red 
Mountain. 
From the following report it will be seen that the great mineral wealth 
of this region is found in a narrow belt of Paleozoic rocks, which are steeply 
upturned against the granite and broken in the most complicated manner by 
a network of faults; that it is along these faults, and proceeding from them 
outward where they traverse calcareous and dolomitic beds, that the princi- 
pal ore deposition has taken place; and that this faulting, which commenced 
with the earliest folding of the sedimentary rocks and has continued to a 
certain extent to the present day, has been most intense and long continued 
on the ridge known as Aspen Mountain, which is so striking to the eye by 
reason of its peculiar form, and which, as the present investigation has 
shown, presents evidence of dynamic disturbance greater than that of any 
