SOUTHERN PACIFIC LINES 239 
of silt,” but much of this is caught in a desilting basin at the Laguna 
Dam, so that it does not clog up canals farther down. 
The limit of area of farm units is 40 acres. The duty of water 
averages 3 acre-feet an acre at the farm, and the irrigation season 
lasts throughout the year. On the rich alluvial bottom lands a great 
variety of crops is grown, but the principal ones are cotton, alfalfa, 
millo maize, kafir corn, feterita, wheat, and barley. A yield of 2 bales 
of cotton to the acre is not uncommon, and alfalfa seed is a profitable 
product which yields as much as half a ton to the acre from two cut- 
tings. For hay, however, the alfalfa may be cut six or more times a 
year. There is a large acreage of pecan groves, some of the older 
trees producing as high as 180 pounds of nuts. The bottom lands 
are protected from overflow by levees and drained to prevent accumu- 
lation of mineral matter by evaporation. 
From Yuma a trolley line runs south down the Colorado Valley as 
far as Gadsden, passing west of the irrigation settlement of Somerton 
(population 891). 
In the valley filling along the Colorado River above the Laguna 
Dam there is considerable fossil wood, which is often brought into 
Yuma. The larger logs are a few feet long and less than a foot in 
diameter. Many of them show grain and ring structure in a very 
striking manner. They are said to be closely related to some of the 
present-day desert hardwoods. 
YUMA, ARIZ., TO LOS ANGELES, CALIF. 
The Colorado River is crossed on leaving Yuma. This great river 
rises in the mountains of Colorado and after its junction with the 
Green River from Wyoming it receives the drainage 
Colorado River. of a wide area in the high plateaus of Utah, New 
Mexico, and Arizona. It was discovered by Fran- 
cisco de Ulloa, who in 1536 ascended the Gulf of California to the 
great mud flats at the mouth of the river. In 1540 it was explored 
by Melchor Diaz, who traveled overland from Sonora, Mexico, to 
the vicinity of Yuma, and by Hernando Alarc6én, who came in boats 
from western Mexico and ascended the river for 15 days, possibly as 
far as Needles. Early in 1605 Juan de Ofiate reached the river in 
the vicinity of Yuma on a trip from Santa Fe. Owing to the custom 
of the natives of carrying firebrands in winter with which to warm 
themselves, Diaz named the stream Rio del Tiz6n (Firebrand River), 
a name more distinctive than the present one. The name “Rio 
Colorado del Norte” was first used on Kino’s map in 1701. He 
reached it first in 1699. Padre Sedelmaier was there in 1744. The 
6 According to investigations by the | per cent, but the average amount is 
Bureau of Reclamation, in times of | 0.7 per cent, or 30 times as much as 
freshets the silt may be as much as 2 | is earried by the Ohio River. 
