SECTION OF WALL OF HIGH MESA. 59 
Nearly one hundred miles southeast of the line where our route crosses this high mesa it has 
been burst through by volcanic force, and though much upheaved, is less broken and disturbed 
than might have been expected. It is there deeply buried under the accumulations of erupted 
material which compo3e and surround San Francisco mountain 
The soil of this elevated district is usually fertile; sustaining dense forests of yellow and nut- 
pine, Douglas’s spruce, and cedar, interspersed with large areas covered with a vigorous growth 
of grama or bunch grass; the contrast which this mesa country presents, in its vegetation 
and geological structure, to the volcanic and desert region of the lower Colorado, was most 
agreable to us in many respects. We had all been wearied by the monotonous prevalence of 
the products of a single destructive force; and the varied and beautiful volcanic minerals so 
profusely scattered over the Colorado basin, devoid of all traces of organisms, and associated 
with the death-like sterility now pervading all that area, had ceased to excite a pleasurable 
scientific interest, and had even produced a positive thirst for life! a longing to reach some 
region where nature’s vital fires had not all burned out; where the varied forms of recent animal 
and vegetable life adorned the earth’s surface, and the rocks below contained in their fossils a 
record of its prevalence on sea and shore from the earliest ages. 
ze Seer Bluish-gray cherly limestone. 
LE ; Light-bronn laminakd and 
cross—stralified Sandstones. 
LA 
i |Blood-red calearcous Sand- 
~| slones wilh gypsum. 
| 
san | is 
oie tt } 
Fia. 14.—sEcTION OF MESA WALL AT CAMP 70. 
Red calcareous sandstones and shales.—Just before reaching the edge of the high mesa we left 
the surface of the Mountain (?) limestone, and came upon a series of blood-red calcareous sand- 
stones and shales, which have an aggregate thickness of nearly 500 feet. This series covers a 
belt several miles in width, bordering the wall of the high mesa and reaching up to form nearly 
half itsgeight. 
Although I examined these red rocks in several localities where fully exposed, I was not able 
to detect in them any traces of fossils; their mineral constituents are, however, of interest; 
affording a marked example of the companionship of peroxide of iron with gypsum, which is 
noticeable in strata of all ages, and to which I shall have occasion again to refer. At our camp 
69, interstratified with the red shales and sandstones, is a thin stratum of cream-colored saticee™s 
limestone, also without fossils. 
Brown laminated sandstone.—Overlying the last-mentioned series, and forming the middle 
portion of the mesa wall, is a group of sandstones of a lighter color, and more purely silicious, 
having an aggregate thickness of over 200 feet. Like the last, these rocks seem to be entirely 
destitute of fossils. I subsequently had an opportunity of examining these sandstones in the 
cafion of Cascade river, fifty miles northeast of the point where I first observed it, and still later, 
in the valleys of Partridge and Cedar creeks, about the same distance west of the San Francisco 
mountain. In the cafion of Cascade river they are somewhat more massive and of lighter color; 
on Partridge and Cedar creeks slightly darker than here; but in all these localities their 
