No. 2. 
REPORT OE EXPLORATIONS EROM PIMAS VILLAGES TO RIO GRANDE. 
CENTRAL SECTION 32d PARALLEL ROUTE. 
Section 1. GENERAL DESCRIPTION OF ROUTE. 
The central section extends from Mesilla, on the Rio Grande, to the Pimas villages on the 
Gila, and comprises that district of country recently acquired from Mexico hy the Gadsden 
treaty. The practicability of constructing a railroad through this section was demonstrated 
hy the data obtained during an examination made hy me in February and March, 1854. 
But, owing to the limited means placed at my disposal, that examination was necessarily 
partial and hurried. Still a practicable route was then determined and reported upon, and at 
the same time lines were indicated for further explorations, by following which, it was pre¬ 
sumed that obstacles encountered on portions of the main line would he avoided, and great 
advantages he gained in regard to the supply of water. 
The line of survey of 1854 commenced at the Pimas villages, on the Rio Gila, and pursued 
a southeasterly course for about seventy miles to Tucson, where an easterly course was assumed 
and pursued until we struck the Rio Grande at Mesilla, opposite Fort Fillmore. Of this district 
the most remarkable feature is the extended, elevated plain lying between the Rio Grande on 
the east, and the San Pedro, a tributary of the Gila, on the west. This plain is made up of a 
series of smooth slopes, converging to several central depressions or basins, and is studded with 
precipitous and rugged ridges and peaks, rising abruptly from the prairie land in picturesque 
confusion, without any apparent order or system. These ridges and peaks, the “Lost Moun¬ 
tains” of the great west, are not, however, without order or system in their arrangement, hut, 
on the contrary, have a decided and marked parallelism in the trend and direction of the axes, 
which have a general northwesterly and southeasterly course. They are, on the one hand, the 
terminal spurs, or representatives, of that portion of the Rocky Mountain system which forms the 
western boundary of the Rio Grande valley of New Mexico, and on the other hand, the incep¬ 
tions or initials of the great Sierra Madre of Mexico. These two mountain chains, with this 
intervening plain, form the divide between the waters of the Gulfs of Mexico and California, and 
become in their prolongation the hack hone or main watershed of the continent, one of the 
great obstacles in the location and construction of the railroad to the Pacific. Owing to the 
wonderful smoothness of this plain, and absence of continuous ridges and watercourses, it is 
impracticable to trace, without detailed and very extended surveys, the exact divide or connect¬ 
ing link joining the axes of the mountain masses. 
By the survey of 1854, the greatest elevation to he encountered in traversing this plain was 
about 5,000 feet, and hy additional data, obtained during the spring of 1855, this has been 
reduced, so that this table land affords a route of transit from the waters of the Atlantic to 
