14 CONCLUSION OF THE OFFICIAL REVIEW, ETC. 



iu the office. This source of error could be 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 be 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 bhe 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 be 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. 



