THE STORY OF OUR PUBLIC DOMAIN 67 



of cheap mining of rich oxidized ores at the surface, 

 more expensive but highly profitable mining of en- 

 riched sulphides at greater depth, and finally min- 

 ing of lean primary ores at lower levels, where costs 

 of recovery even with the best modern methods may 

 soon exceed the market value of the product. 



"But as time has passed fewer and fewer new 

 deposits have been found. The hills have been pros- 

 pected over and over by the old-time methods from 

 base to summit, from Canada to Mexico, and from 

 the Great Plains to the Pacific. An occasional strike 

 has been made within the last third of a century 

 Cripple Creek in 1891, Tonopah and other Nevada 

 camps in 1900 and later but by far the greater 

 number of the big metal mines of the United States 

 were in operation within two generations after the 

 discoveries in California. The finding of new ore 

 bodies is becoming more difficult, and the difficulty 

 may be expected to increase. The problem of main- 

 taining production involves increasing skill in ore 

 finding and increasing use of lower-grade material. 

 The first is the problem of the geologist and the min- 

 ing engineer ; the second is the problem of the metal- 

 lurgist and the industrial organizer. 



"The leaders in the mineral industry are acutely 

 aware of the necessity of finding more ore, even 

 though the rest of the world may be oblivious to 

 this need." 



With revision of land office work and reduction 

 of offices and personnel to meet the altered condi- 



