132 GUIDEBOOK OF THE WESTERN UNITED STATES. 
and still preserves its nearly level surface. The lava sheet that caps 
the high hill on the north side of the canyon below Wolcott was prob- 
ably once a part of this same flow or flows but has been separated 
from it by the canyon cut by Colorado River. 
After passing milepost 342 and a small cut a few hundred yards 
beyond the railroad track reaches the bank of Colorado River, which 
it follows to the western border of Colorado. This 
Dotsero. art of the country is noted for its cattle and 
Nate te, feet. horses, and the siding of Dotsero is maintained 
largely for their shipment. There are no red rocks 
in the valley of Colorado River just below the mouth of Eagle 
River, but the rocks there exposed are about as hard as the soft 
red and green shale and sandstone above. At first the traveler 
may not be able to identify any of the dull-gray and slate-colored 
rocks below Eagle River with those he has seen farther upstream, 
but a comparison of the section and of the order of the formations 
may show him that these beds are the same as the heavy cliff-making 
sandstone and shale which he saw just below Minturn. It might be 
supposed that the same formation should show the same composition 
and hardness wherever it is exposed, but as these formations con- 
sisted originally of sand, clay, and limy materials that were de- 
posited in some body of standing water, either a lake or the sea, it 
is apparent that the character of the formation at any place must 
depend largely upon the kind of material there swept into the body 
of water by the streams, and as the land near by was probably com- 
d of various kinds of rocks, which furnished various kinds of 
material, it does not seem strange that at one locality a formation 
may consist largely of sandstone and at another of shale. Changes 
from sandstone or shale to limestone are more rare, but such changes 
are observed in many parts of the country. The soft materials, in- 
cluding some coal beds that are exposed below Eagle River, belong 
to the Weber formation, which is in the lower part of the upper Car- 
boniferous rocks. 
The rocks rise gently westward, and at milepost 345 the massive 
layers of the Leadville limestone rise from river level. This point 
marks the beginning of one of the most noted canyons on the line 
of the Denver & Rio Grande Western Railroad, the canyon of Colo- 
rado River that stretches in unbroken beauty and grandeur from 
this point to Glenwood Springs, a distance of 15 miles. (See Pls. 
LVI, 2, LVI, and LIX.) This great canyon was trenched by the 
river in an immense upfold of hard beds, which include all the sedi- 
mentary rocks that the railroad has crossed in the canyons above, 
and into the underlying granite, to a total depth of 800 to 1,000 feet. 
The first appearance of the Leadville limestone, noted above, neat 
milepost 345, is marked by a warm sulphur spring, very similar to 
