6 
SURVEY OF THE COLORADO OF THE WEST. 
it would be necessary to establish depots for supplies at a number of 
points along the course. 
Between Gunnison’s Crossing, on Green River, and the foot of the 
Grand Canon of the Colorado, a distance of five hundred and eighty- 
seven and one-half miles, it was not known that the river could be 
reached at more than two points. One of these, at the crossing known 
as El Yado de los Padres, where Father Escalante had crossed the river 
in 1776, by following an old Indian trail; the other but a short distance 
below, at the mouth of the Paria River. This route had been discovered 
by Jacob Hamlin, a Mormon missionary. These were so near together 
that only one of them could be used as a depot for supplies. 
The last part of the year 1870 was given to the exploration of routes 
from the settlements in Utah to the Green and Colorado on the east 
and Colorado on the south. These lines of travel were mapped by fix- 
ing astronomic stations with the sextant and connecting them by the 
methods usually adopted in a meandering reconnaissance. 
Early in the spring of 1871 boats were provided at Green River Sta- 
tion. The latitude of this point was determined by observations with 
the zenith telescope, and the longitude by telegraphic signals, with an 
astronomic station at Salt Lake City, previously established by officers 
of the United States Coast Survey. The altitude of this point above 
the sea had also been determined by the railroad surveys, so that the 
altitude, latitude, and longitude of the initial point of the survey were 
fixed with a good degree of approximation. 
In descending Green River, astronomic stations were established at 
distances averaging forty-five miles by river, or about twenty-five miles 
by direct lines, the instrument used being the sextant. At each of these 
stations the variation of the needle was determined. The river was 
again meandered by two observers, working independently, and their 
work compared. 
The lines between stations on the river were used as a series of base- 
lines, the lengths, of course, only approximately determined, and an in- 
tricate net-work of triangles was projected to salient points on either 
side of the river. From a vast number of points thus fixed, the surface 
contour of the country was sketched so as to include a belt from twenty 
to fifty miles wide, the parties making frequent trips from the river into 
the interior of the country. At each of these astronomic stations bar- 
ometric readings were recorded in hourly series, and as we proceeded 
down the river tri-daily barometric readings were made, all referred 
to the water’s edge. With the river as a base-line for hypsometric work, 
altitudes were determined by triangulation and by barometric methods, 
using both mercurial and aneroid instruments. Thus all of our altitudes 
in this region are related to the river. 
Our time during the spring, summer, and fall of 1871 was thus occu- 
pied until we arrived at the mouth of the Paria, a stream entering the 
Colorado from the northwest, a little below the Arizona line. 
