CLASSIFICATION IN BELATION TO WATER KESOURCES. 159 



lands in. New Mexico, of a great unconformity which separates into 

 two formations a great thickness of strata that had hitherto been 

 considered as a unit. This discovery is important not only on account 

 of its strictly scientific bearing, biit because it indicates that high- 

 grade coking coal occurs in rocks of comparatively recent (Eocene) 

 age. 



It therefore appears that much important and diversified informa- 

 tion is obtained in this way. Science is continually garnering facts 

 against the time when their economic importance will appear, or 

 when they may be correlated with other facts to furnish a broad 

 hypothesis which may profoundly affect methods of prospecting or 

 developing some mineral, such as oil. In addition, much local infor- 

 mation of direct and immediate value to the mine operator or pros- 

 pector is so gathered. Finally, the best obtainable record of the 

 topography, water resources, and soils of the area examined is 

 officially made. While the classification of public land is the im- 

 mediate object of the work described in this bulletin, it is evident 

 that such work, because of its exacting requirements as to accuracy 

 and thoroughness, furnishes the best possible basis for valuable scien- 

 tific generalizations. 



CLASSIFICATION IN RELATION TO WATER RESOURCES. 



GENERAL PRINCIPLES OF WATER UTILIZATION. 



One of the most important factors in the development and use of 

 the remaining public lands within the United States is water supply. 

 The development of power, the extension of agriculture and grazing, 

 the growth of mineral industries, transportation, and various other 

 activities depend directly on the quantity and quality of the under- 

 ground and surface waters in what is, generally speaking, an arid 

 region. To dispose of or to administer the remaining public lands 

 without reference to their water supply is to ignore that natural 

 resource which will, perhaps more than any other, affect their future 

 utilization. 



Water is unique among the mineral resources of the earth in that, 

 within natural limits, its supply is continually replenished and is there- 

 fore, in a large way, inexhaustible. That is to say, Avithin the limits 

 of the natural yield of a basin a certain minimum quantity of water 

 will be available year after year in any river channel for irrigation, 

 for city supply, or for power, as may be required. Aside from the 

 inherent value of the water, the ownership of an important source 

 of water supply becomes of the greatest consequencCj for such owner- 

 ship carries with it a measure of control, for an indefinite time, of 

 all industries dependent on that particular source. 



