CHAPTER XXIV. 



or THE PERMANENT SUPPLY OF WATER, AND OF THE FEASIEILITY 

 OF OBTAINING ABUNDANT SUPPLIES BY ARTESIAN BORLNGS. 



Only a portion or the houte deficient in the supply of water. — Extent of this district. — Geological summary. — Meteor" 

 OLOGY. — Region of summer rains. — Elevation of the district. — Annual fall of rain. — Causes of the diminution of bain 

 TfESTWARD.— Quantity absorbed by the soil. — Contrast of a north temperate and an inter-tropical zone. — Substitutes 

 for artesian wells. — Water tanks.— Ordinary wells.^ — General conclusions. — Localities of natural su ^ ly on route. — 

 Cook's spring. — Rio mimbres. — Ojo de la tacca. — Valle del sauz — Playa de los pimas. 



Along parallel 32°, the shortest route by which the Pacific can be reached, the difficulty 

 of obtaining water is one which is shared in common with any other travelled road over the 

 continent more northward, and a difficulty which, regarding the route itself, may be obviated. 



It is only over a portion of the route in which the deficiency of water is felt ; it is to this 

 locality only that attention will be directed, and if it can be shown that in these less favored 

 districts a sufficient supjDly of water can be had the argument applies a fortiori to the whole 

 route. 



This district is comprised between the Rio Bravo and the San Pedro, a distance of 253 miles ; 

 is not traversed by any large river, nor siibject to a large fall of rain; to arrive at any conclu- 

 sions concerning the facility of obtaining water sufficient for railroad wants, two classes of cir- 

 cumstances will require to be noticed. 



1. The geological conditions. 



2. The meteorological conditions. 



1. Geological. A detailed description of the structure of the region has been given, and the 

 sections appended illustrate the description. It is unnecessary, therefore, here to state more 

 than that the first 85 miles west of the Eio Grande is broken up by basaltic upheavals and 

 overflows ; that from Cook's spring to PeCascitas succeeds a district which, though not so 

 broken^ is yet traversed by porphyry upheavals, producing faults, and having horizontal strata 

 only over very small areas, so small as not to be conveniently tapped. 



The elevated lands of Penascitas and Ojo de la Vacca are the foot hills of a chain of igneous 

 rock, (Burro mountains,) which lie northward. These lands are the dividing ridge of the 

 waters of the continent along this parallel ; those on the east running southward into the Gulf 

 of Mexico, and those on the west rolling north (via the Gila) into the Gulf of California. 



West of these elevated lands the country drops by a succession of troughs or valleys, sepa- 

 rated from each other by short unconnected ranges of felspathic and granitoid rock, running 

 N.N.W. and S.S.E. These valleys or flats have their rock basis of carboniferous limestone 

 and overlying sandstones, and are four in number ; 



1. Small valley, with lagoons, 



2. Valle de los Playas. 



3. Valle del Sauz. 



4. Playa de los Pimas. 



