_ Scoria, extend from the river to Chimney Peak. 
= hi ne * eee Be ict loubl 
emery 
Colorado River of the West. 401 
of that series, a sandstone, everywhere affords striking evidence of current 
action in its cross stratification. 
In harmony with this fact is the occurrence of true coal measures with 
beds of coal, indicating emerged land at that epoch, north of the Colo- 
rado, at no great distance from this locality. 
Hence the theory generally received that the formation of the continen 
began in a nucleus about Lake Superior, and that the places of the Rocky 
and California mountains were, until the Tertiary period, occupied by an 
open sea is proved untenable.” 
The engraving on the opposite page showing Chimney Peak 
_ Tange is thus described: 
“Above the mica slate hills, red, white, green, pink, and blue tufas, 
_ porphyries, and trachytes, described as occurring below, reappear, giving 
the same fantastic appearance to the scenery. These rocks, with trap and 
- } hich ernwne 
ea 18 2 
- &mountain chain, probably the northwestern prolongation of the middle 
. _ Tange of the Purple Hills. Like the other peaks of the range it is com- 
~ lumnar summits exhibited by all the mountains of this vicinity. Dome 
— of trap, and affords a striking example of the tendency to form co- 
onntains on the east of the Colorado, present the same features in nearly 
an equal degree. The mountains which have this form are all trappeau 
~ in character, and doubtless owe their peculiar outlines to the manner in 
uently occurs, these | 
lowing streams, perpendicular walls are formed, and large masses usually 
exhibit mural faces. This will account for the peculiar outline which 
_ Many of the trappean summits of the mountains of the Colorado basin 
Present. at altitude, as compared with the mass of the range 
Which they crown, is doubtless due to the resistance offered by their 
| ' ces which have removed perhaps sev- 
ing tufas and trachytes once surround- 
oma 
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2. 
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which the highly colored rocks before 
cribed are very conspicuous, and extend for many miles along the base 
of Chimney Peak range. ; : 
“At tntertah the sedispentary rock is covered with erupted materials, 
basaltic trap, scoria or ashes; and at several points are cones, age rye 
Yoleanic vents, and the sources from which these igneous rocks were de- 
Am. Jour, Sct.—SEconp Serres, Vou. XXXII, No. 99.—May, 1862. 
51 
