PREFACE 



Two of the great industries of the Rocky Mountain region, 

 both of which have developed within comparatively recent years, 

 are copper mining and irrigation farming. Commercially, these 

 important industries have every reason for harmony with each 

 other. The operations of the copper miner build up busy cities, 

 initiate improvements in transportation and develop populations 

 which must be fed. The irrigation farmer, on the other hand, 

 produces abundant and wholesome supplies of foodstuffs upon 

 which copper-mining communities depend and in return for 

 which they pay good prices. Incidentally, however, to the rapid 

 expansion of these two industries in Arizona and elsewhere in 

 the west, points of contact have developed requiring adjustment. 

 One of these has been in connection with the disposition of min- 

 ing wastes, including smelter gases and tailings from which 

 the values have been abstracted. In relation to tailings, enormous 

 quantities of which are produced from low-grade ores, consider- 

 able study has been devoted in Arizona by scientific agencies and 

 by the copper companies themselves, to the problem of their 

 satisfactory disposal. The object of such disposal is, on the one 

 hand, to keep injurious substances, both insoluble and soluble, 

 away from irrigated crops and, on the other hand, to make some 

 use of them by the mines themselves. 



The result of these studies has been, thus far, to devise 

 economical means for impounding almost the whole of the solid 

 wastes from some of the mines, thus avoiding injury to sub- 

 jacent lands and conserving such values as may yet remain 

 unextractecl in the ores. It seems likely, in fact, that by means 

 of improved methods now under consideration, these values may 

 be economically reclaimed. 



The question of the toxic effects upon crops of soluble salts 

 of copper which cannot be withdrawn from solutions that escape 

 into irrigating streams, is the one with which this publication is 

 mainly concerned. 



The outcome of the attention which has l^een devoted by 

 farmers and copper companies to the "tailings question" in 

 Arizona is a happy solution of a once formidable controversy; 

 and the establishment of a precedent wiiich will be of great 

 value in time to come in the adjustment of similar differences 

 throughout the Rocky Mountain region. 



