SOUTHERN PACIFIC LINES 173 
Pedro River to Benson. This road became part of the great emi- 
grant trail of the West, and its existence and relations to a possible 
railroad route had much to do with the Gadsden Purchase. 
In prehistoric times the part of San Bernardino Valley near the 
springs was occupied by Indians who lived in settlements of consid- 
erable size. According to Sauer and Brand, there are many remnants 
of foundations and “‘cimientos,”? or cobblestone walls, and abundant 
fragments of pottery, implements, ornaments, and a few corn cobs; 
potteries of various types indicate long occupation and commerce far 
to the north, south, and east. Probably mesquite beans were the 
most important food element to these people, but they raised crops 
on some of the more favorable soils. 
Beyond Perilla siding the railroad skirts a lava-covered mesa and, 
leaving the broad San Bernardino Valley by a huge horseshoe bend, 
ascends the rocky valley of Silver Creek to a divide at Cazador siding. 
(See sheet 21.) Near Silver Creek siding sand and conglomerate are 
exposed under the lava sheet, and voleanic rocks of Tertiary age 
appear. These rocks present striking exposures in the ridges about 
South College Peak, where there is a cap of massive latite with strongly 
marked columnar structure on a large scale. A feeder dike trending 
east from the foot of the ridge is noticeable 1% miles south of Silver 
Creek siding. Near Cazador siding Castle Dome, a huge plug of 
latite, is visible 5 miles to the north. From this point the course of 
the railroad is mostly south and southwest over Tertiary volcanic 
rocks. 
At Lee siding the railroad passes between two knolls of limestone of 
Comanche age, which underlies or is faulted against the volcanic 
i rocks, and enters the southern portion of Sulphur 
Elevation 4,411 feet. Pring Valley. In this vicinity this valley is drained 
New Orleans 1,30 by Whitewater Creek, flowing southeast into Mexico, 
= where it finally empties into the Rio Bavispé, a branch 
of the Yaqui River, which empties into the Gulf of California near 
Guaymas. 
On approaching Douglas the first visible objects are the high stacks 
of the two large smelters, the Copper Queen and the Calumet & 
: Arizona, on the western edge of the city, where copper 
fen oso eet, OFS from Bisbee and other places are treated. Doug- 
Population 9,828. las lies near the middle of the wide plain of the south- 
New Cumans #8 ern extension of Sulphur Spring Valley. The valley 
: plain here is about 20 miles wide and extends north- 
ward 60 miles to and beyond the main line of the Southern Pacific 
Railroad in the Willcox repaints (See P. 156.) It is deeply £ seierbael ‘by 
sand and gravel washed from th lop d known 
to be nearly 1,000 feet thick. “The configuration o of these intermon- 
tane valleys is highly characteristic, the : oping gently 
