SURVEY OF TIIE COLORADO OF THE WEST. 
1 !) 
Such are some of the facts brought to light in the great section made 
from Green River Station to the mouth of the Bio Virgcn. 
It has already been seen, in the account given of the geographic work, 
that a much greater length of time was expended in the studies made 
on land than in those made on the river. 
A geological section has been made from the Grand Wash to the Ver- 
million Cliff, west of Marble Canon, near the parallel of 36° 30'; another 
from the Colorado River west to the Pine Valley Mountains, near the 
parallel of 37° 30'; another from the Sevier River east across the Wa- 
satch Plateau, and still on to Green River. One has been made along 
the course of the Paria from its source in the Pauns-a-gunt Plateau to 
its mouth, including rocks from the Tertiary age to the summit of the 
Carboniferous. Another has been made from the Pauns-a-gunt Plateau 
south along the course of the Kanab to its mouth, representing rocks 
of ages extending from the Tertiary to the base of the Carboniferous. 
Still another has been made from the summit of the Mar-ka-gunt 
Plateau, down the Rio Virgen to its mouth, embracing a series of rocks 
from the Tertiaries through the Carboniferous, Devonian, and Silurian 
into the schists. 
In addition to these general or running sections, numbers of vertical 
sections have been made for the purpose of giving the details of stratifi- 
cation. 
PLAN OF SECTIONS. 
The plan for these sections is as follows : The base-line at the bottom 
of the section represents the level of the sea; the line immediately 
above this, and parallel to it, represents the altitude above the sea of* the 
lowest point observed in the section; the upper line represents the 
highest point. The meandering line between these points represents the 
line of lowest observation in the escarpments seen along the course of 
the chasms through which the sections are made, and a reference to the 
scale gives the altitude of any point along this line above the level of* 
the sea. 
r. 
Between this meandering line and the upper line the section is so 
constructed with colored bands as to represent the general facts of geo 
logical structure, i. 6 ., the succession of geological formations and many 
important facts of stratification, and the faults, folds, and nonconformi- 
ties; and these colored bands are so arranged as to represent the mag- 
nitude of the escarpment which has been studied, and the altitude of 
the upper line of the section above the level of the sea, so that the high- 
est as well as the lowest line above the sea can be determined by refer - 
ence to the scale. * 
Thus the sections not only represent the structural geology, but also 
constitute a double profile ; the lower profile or lower line of observa- 
tion being the profile of the bottom of the canon, the upper line the pro- 
file of the summit of the wall, and the two combined the proper longi- 
tudinal profile of the cation itself. 
