202 EXPLORATION OF THE CANONS OF THE COLORADO. 
Since these vermilion beds were stripped from the adjacent country, 
the few showers of this arid region condense chiefly about the summits of 
the mountains, and the waters, gathering into streams, and running down 
into the lower region, have cut deep gulches through the sheets of basalt, 
in many places revealing the structure of the mountains themselves. The 
last puff in these . eruptive vents tossed high into the air scoria and ashes ; 
the lighter materials were carried away by the winds, the heavier fragments 
fell, and thus cinder-cones were piled up; and in many of these cinder- 
cones the Outlines of the craters are still preserved. 
The beds of lava are of various ages. The first were poured out in 
that ancient time before the sandstones had been carried away. From time 
to time new beds were formed, and the latest beds have been poured out in 
a time so recent, that the very waves of the congealed floods are still pre 
served, and there is no reason to suppose that this action is completed. In 
time another vent may be opened, and another river of red hot rock gush 
from the earth. Nor are all the cones of late origin ; each outflow of molten 
matter seems to have ended in the formation of a cone. In the elder beds 
the cones have been washed away, but their sites are marked by scattered 
cinders. In the very latest cones the craters are still preserved, and their 
cinders are angular fragments of slag, that show that many storms have not 
fallen upon them since they broke in cooling. 
So, even these eruptive mountains were hewn from the rock, and only 
the cinder-cones, scattered here and there, small in comparison to the great 
mountain masses, were piled up in their present forms. 
It is probable that the cones have cores which extend to great depths, 
and perhaps connect the sheets of basalt above with masses of like material 
below, and thus the more enduring and protecting beds to which these 
mountains owe their preservation are anchored to the heart of the earth. 
METHODS OF EROSION. 
In this and the foregoing chapter I have attempted to describe the agen 
cies and conditions which have produced the more important topographic 
features in the Valley of the Colorado. These features are mountains, hills, 
hog-backs, bad-lands, alcove lands, cliffs, buttes, and canons. The primary 
