14 
CONCLUSION OF THE OFFICIAL REVIEW, ETC. 
in the office. This source of error could he obviated by a preconcerted arrangement with an 
observatory for observations, at certain times during the continuance of exploring parties in 
the field. 
Upon reviewing his barometrical work for the correction of errors due to abnormal changes, 
Captain Whipple has included a mass of altitude observations, not reduced before for want of 
time, which gives a remarkably detailed and accurate profile of the ground; and in connexion 
with the equally minute topographical notes, now for the first time used, has greatly improved 
the character of his route as a railroad line. 
Among the most important changes that the revision has introduced, Capt. Whipple reports 
the reduction of the length of the route, which from Fort Smith to San Pedro is now 1,760 miles, 
and from Fort Smith to San Francisco, direct from the Mojave river by the Tay-ee-chay-pah 
pass, avoiding the tunnel of the Cajon pass, it is 2,025 miles. In the preliminary report the 
distances were measured upon the wagon trail; those now given are along the plotted railroad 
line. Many of the difficulties of construction previously reported may, in the judgment of Capt. 
Whipple, be obviated; and, in his opinion, there is strong probability of improving the route still 
further, by shortening distance and avoiding costly construction. A scrutiny of the baro¬ 
metrical observations through Campbell’s pass of the Sierra Madre, about twenty miles north 
of the Camino del Obispo, shows that that mountain chain may he crossed without a tunnel or 
excavation at the summit, with a maximum grade of 40 feet to the mile, at an elevation of 
6,952 feet above the sea. By the Camino del Obispo, the old route, elevation 8,250 feet, a tunnel 
three-quarters of a mile long, at an elevation of 8,000 feet, was required. 
The elevations of several of the passes have been materially reduced; and Captain Whipple 
reports that the data are now provided for an actual computation of the excavation, embank¬ 
ment, and cost of construction of the proposed route. 
As this computation necessarily involves much tedious labor, it has not yet been made, and 
for the present Captain Whipple submits an estimate made in a manner similar to those of the 
other routes, in order to exhibit more correctly the comparative practicability of this, than was 
done in the preliminary report. He has based it upon the facts developed by a careful study of 
the observations made and the material collected in the field, and it is believed by him that the 
amount will he much diminished when the results of the computation are arrived at. The cost of 
construction, as given in the preliminary report, was greatly exaggerated, the estimates having 
been formed without reference to the field notes. In the examination which, by your direction, 
I made of that report, the estimates were thought by me to be largely in excess. They were— 
From Fort Smith to San Pedro, distance 1,892 miles. $169,210,265 00 
From Fort Smith to San Francisco, the road leaving the Mojave river 34 miles 
from the east entrance of Cajon pass, and crossing the Tay-ee-chay-pah 
pass, (the estimate from the Mojave river to San Francisco, a distance of 
406 miles, having been made by me) distance 2,174 miles. 175,877,265 00 
These, according to Captain Whipple, are now— 
From Fort Smith to San Pedro, distance 1,760 miles. 86,130,000 00 
From Fort Smith to San Francisco, crossing direct from the Mojave river to 
the Tay-ee-chay-pah pass, distance 2,025 miles. 94,720,000 00 
Under the appropriation for continuing explorations and surveys to ascertain the most prac¬ 
ticable and economical route for a railroad from the Mississippi river to the Pacific ocean, three 
parties were organized by your directions. 
