CHAPTER I. 
OBSERVATIONS UPON THE MOUNTAIN RANGES AND GENERAL RELIEF 
OE THE SURFACE ALONG THE ROUTE. 
Direction and length of the line.—Barometric profile.— Six principal chains crossed by the survey.—Sandia and santa 
fe ranges.—Sierra madre.—Aztec and aquarius ranges. -Cerbat ranges.—Ranges along the Colorado.—Pai-ute 
ranges.—Bernardino sierra.—Mogoyon sierra.—Elevation produced by the volcano of san Francisco.—Table-lands, 
plains, mountain slopes, and valleys.—Character of the eastern slope of the anaiiuachian chain near the line of sur¬ 
vey.'—Llano estacado.—Bluff borders of the llano.—Its extent and mean elevation.—Plain between the santa fe and 
ALBUQUERQUE MOUNTAINS, AND THE SIERRA MADRE.—ITS CHARACTER AND AVERAGE ELEVATION.-TABLE-LANDS AND SLOPES WEST OF 
THE SIERRA MADRE.-EXTENT WEST AND NORTH.-TlIE SLOPE ON THE WEST MORE GRADUAL THAN ON THE EAST.—§TAIR-LIKE DE¬ 
SCENTS.—General elevation.—Yal del china.—Yalley of hawil-hamook.—Its deep narrow character.—Plain or 
VALLEY BETWEEN THE CERBAT RANGE AND THE COLORADO RIVER.-VALLEY OF THE COLORADO.-GREAT BASIN.-ITS GENERAL CHAR¬ 
ACTER FORMED BY A COMBINATION OF SHORT RIDGES AND SLOPES -INCLINATION OF THE SLOPES AND THEIR ORIGIN.—PLAIN AND VAL¬ 
LEYS BORDERING THE PACIFIC. 
Before commencing the observations on the geological structure of the line surveyed hy Lieu¬ 
tenant Whipple, I propose to enumerate in a very brief manner the principal physical features 
of the route, and to give a general view of the configuration or relief of the surface, based 
chiefly upon the results of Lieutenant Whipple’s survey, and the barometrical profile which is 
presented with his report. For full and complete information on the topography and general 
features of the route, reference should he had to that report. The following summary is in¬ 
tended merely as an introduction to the geology, and as a guide to the location of the geological 
phenomena which are described in the report. 
The line surveyed follows, as has been indicated, the vicinity of the 35th parallel of latitude, 
and extends from Fort Smith, Arkansas—a point nearly due west from Memphis, Mississippi— 
westwardly to the Mojave river, and thence southwestward to the Pacific ocean, at San Pedro. 
The distance thus traversed is 1,892 miles, and the route is included between the meridians of 
94°.26 and 118° 16'. From the Mississippi river, Fort Smith is reached hy the navigable 
waters of the Arkansas river. The valley of the Canadian, which is properly a continuation of 
the Arkansas, is then followed for the greater part of the way to its head-waters at the eastern 
foot of the ranges of the great central mountain chain of the continent. This chain is crossed 
near Albuquerque, through the San Antonio Pass, about forty miles south of Santa Fe. Cross¬ 
ing the valley of the Bio Grande, the survey reaches the Sierra Madre one hundred miles west 
from Albuquerque. This range is traversed near latitude 35° hy “ Campbell’s Pass,” and one 
further south called Canrino del Obispo; and the village and ruins of Zuni are reached at its 
western base. From Zuni, the valleys of the u Puerco of the West” and the Colorado Chiquito, 
the waters of which flow into the Pacific, are followed to the base of the great extinct volcano 
called San Francisco Mount, about three hundred and fifty miles west from Albuquerque. As¬ 
cending over the lavas of this mountain, the line passes the Aztec mountains and reaches the 
Aquarius range, which forms the eastern border of the valley of the Hawil-hamook or Bill 
Williams’ fork of the Colorado river. Crossing that range through Cactus Pass, in longitude 
113°, the valley of the river is reached and followed southeasterly for about seventy-five miles, 
then turning westwardly to its junction with the Great Colorado river in latitude 34° IT'. 
Passing up the valley of the Colorado, nearly to the 35th parallel, the survey again turns 
Is 
