ON THE SUPPLY OF WATER. 
31 
On the San Pedro route water is abundant and convenient, at Chameleon spring and Prospect 
creek, and in the entire valley of the Eio San Pedro. Besides these permanent supplies, water 
is found, after the rains, on th q play as and in depressions in the drains. 
Lieut. Andrews, the commanding officer of the escort, found several inches of water on the 
Playa de los Pimas on his return to California in the month of October. Col. Hays, during the 
same month of a previous year, camped on the margin of one of the Pyramid playas , then covered 
with water, and called, in Mr. Nugent’s notes of this trip, “ a small lake.” This is doubtless 
the Laguna of Capt. Whipple, a camping place occupied by his parties while engaged upon the 
survey of the boundary under the treaty of Guadalupe Hidalgo. In the bed of the arroyo, at 
the base of the Sugar Loaf, a limited supply of water is had by digging a couple of feet. 
Lieut. Andrews had, on the Tucson jornada, an abundance of water, where not a drop was found 
early in July. These rains, in addition to filling the natural reservoirs, give new life to the 
grasses. The fall and winter months are, therefore, the most favorable for making the trip across 
this country. For the working parties in the construction of the road, during the dry season, 
water can be obtained from the several above mentioned permanent sources of supply, but this will 
involve, of necessity, much haulage, the maximum distance being twenty-three miles. But I am 
clearly of the opinion that water can be obtained at other points along and near the line of 
construction by sinking common wells. These playa formations are particularly favorable. 
Being basin-shaped, they receive and retain the drainage from the surrounding country, giving us 
natural reservoirs, which require only to be tapped to give a constant and plentiful supply. 
On the Playa de los Pimas we find springs, located along the line of junction, between the 
surrounding slopes and the bed of the Playa, outlets for the water, which is prevented from 
rising on the lower level by its impermeable bed of clay. 
The fall of rains has averaged, at Fort Fillmore, 9.23 inches per year for three years, but I 
am of the opinion that this is greatly below the average fall of rain for this region. At Fort 
Yuma the average fall for three years has been found to be but three inches. To take the mean 
of these quantities for the fall of rain upon the intermediate plateau, is not, in our opinion, a 
legitimate conclusion, one of the premises, as we shall endeavor to show, being erroneous. The 
register doubtless gives the correct amount of rain for the region about the junction of the Gila 
and Colorado rivers, that locality being surrounded by an inhospitable waste, with no mountains 
sufficiently lofty, within one hundred miles, to arrest the moisture, which, on account of the 
ascending currents of heated air, floats high above the plains. The deposition of rains must 
herefore be light. But it is a notorious fact, that not only at Fort Fillmore, but throughout 
New Mexico and the recently acquired territory, during the rainy season, clouds are seen almost 
daily enveloping the lofty summits of the mountains, distilling copious showers, while not a 
drop is delivered to the plain. In these regions the sky is rarely overcast; and when the 
ascending currents of warmer air from the circumjacent plains arise, and, in connection with 
the southeast winds, convey the clouds across the valleys to. nestle again on some other range, 
rains fall on the plains-and in the valleys in torrents, but of short duration. The registry of 
rain, therefore, at Fort Fillmore, and at other posts or towns in the valley of Rio Grande or 
on open plains to the east or west, must be far below the correct amount. The fall of rain at 
Fort Bliss averaged in three years 11.21 inches. Its situation with reference to Fort Fillmore 
is significant and confirmatory of the views above expressed. Fort Fillmore lies west of the 
Organ mountains, about twelve miles from the summits. Fort Bliss is opposite El Paso, about 
three miles from a high point of these mountains, and a little to the east of their trend. The 
southeast winds, moisturefiadened from the Gulf of Mexico, are deprived of a portion of their 
