226 GEOLOGY OF TRANS-PECOS TEXAS. 



Pitchblende. Silver, native. Tourmaline. 



Pitchstone. Stromeyrite. laic. 



Quartz, granular, glassy, Salt. Tetrahedrite. 



milky, smoky, amethys- Sulphur. Wad. 



tine, aventurine, crystal. Siderite. Wulfenite. 



Serpentine. Selenite. Wolframite. 



Stilpnomelane(f). Sphalerite. 



There are also combinations of copper with lead, uranium, zinc, and iron; 

 tin with lead, etc.; nickel with iron and manganese; bismuth with copper 

 and lead; and many other minerals now awaiting determination in the lab- 

 oratory. 



AGRICULTURE AND IRRIGATION. 



As far as the soil of the flats between the mountain chains is concerned, 

 its fertility can not be disputed. Being composed of the decomposed detritus 

 of the granites, porphyries, and limestone, it does not require any analysis to 

 show its adaptability for agricultural purposes. Mr. Harrington, Professor 

 of Chemistry of the Agricultural and Mechanical College of Texas, was with 

 the survey in Trans-Pecos Texas during the summer, and collected soil speci- 

 mens from the Rio Grande bottom lands, towards the Pecos River, and his 

 analyses confirm the fertility of these soils. These flats of West Texas must, 

 however, be irrigated to secure good crops. Irrigation is not a thing unknown 

 in America, or even in the United States, and it is not a new nor insufficiently 

 tested scheme. Irrigation from the water of the Nile, by streams in the 

 East Indies, by springs and streamlets in Asia Minor, by artesian wells in 

 Algiers, is proof of the practicability and of the beneficial results of irrigation, 

 and has been practiced in some of these countries for thousands of years. 

 Nearer home it is a well known fact that enormous results are obtained by 

 irrigation in Mexico, New Mexico, Colorado, and California — in countries 

 some of which have certainly no more rainfall than the west of Texas. 



During the months of September and October about 1.1 inches of rainfall 

 was shown by the rain gauge in the camps of the survey in El Paso County, 

 and the rainfall from May to September is estimated to be no less. It may 

 have been an extraordinary wet year, but the conditions in which the grass 

 and shrubs were found the fall before last are sufficient proof that about the 

 same amount of rain fell during 1888. 



Excepting Algiers, irrigation by artesian wells is not carried on to any 

 extent; irrigation by rivers in most cases is confined to the river bot- 

 toms or low lands adjacent to the rivers; but wherever in hilly or moun- 

 tainous regions there is considerable rainfall, causing rises in the rivers, and 



