554 University of California Publications in Agricultural Sciences [Vol. 1 



GENERAL AND PRACTICAL CONSIDERATIONS 



The practical as much as the theoretical point of view in- 

 spired these investigations. In a time such as this, when the 

 smelter question is of great significance in agricultural districts 

 and when outcries against the damage caused by both smelter 

 fumes and solid smelter wastes are most insistent, it appeared 

 to us that the moment had arrived for wholly disinterested in- 

 vestigators to examine into it. Our experiments as described 

 in this paper have dealt, in the main, with the effects on barlej' 

 growth in three successive crops of the metals which would be 

 likely to be deposited in the vicinity of smelters and gradually 

 washed down into sources of irrigation water for the territory 

 lying below the smelter plants. Despite the fact that we have 

 used much more soluble forms of the so-called toxic salts than 

 are likely to occur under the conditions just described, and de- 

 spite the fact that we have employed both large and small 

 amounts of these salts, we are unable to read into our results 

 any serious danger to agriculture from the solids of smelter 

 wastes as they may be transported to cropped lands by irrigation 

 water. In making this statement we are not unmindful that 

 ver}" small areas occur^-- near the smelter plants in which the 

 tailings may be carried down by streams and deposited on land 

 in large quantities. These may, for example, carry enough of 

 the toxic heavy metals to render land poor in producing capac- 

 ity. But in the first place the most prejudiced persons will not 

 claim that such affected areas of agricultural land are more than 

 negligible quantities when the question is considered in the 

 large : in the second place, even under conditions so extreme, 

 none but the most biased will deny that proper methods of man- 

 agement can be made to render innocuous any harmful effects 

 which the tailings in question may be potentially capable of 

 exerting. These methods of management are clearly indicated 

 and include the impounding of water carrying tailings or the 

 passage of stream water through screens which will separate out 



122 See E. H. Forbes, ' ' Certain effects under irrigation of copper com- 

 pounds upon crops," Univ. Calif. Publ. Agri. Sci., 1, no. 12, 1917. 



