NEW YORK ACADEMY OF SCIENCES 637 



In order to come within the possible limits of profitable 

 and successful treatment the ores of the more important metals 

 should have at least the following percentages, but that we may 

 grasp the relations correctly, it must be appreciated that local 

 conditions affect the limits. Thus in a remote situation and 

 with high charges for transportation an ore may be outside 

 profitable treatment although it may contain several times 

 the percentages of those more favorably situated. Iron ores 

 in particular which are distant from centres of population 

 are valueless unless cheap transportation on a very large scale 

 can be developed, while gold in an almost inacessible region, 

 like the Klondike, may yield a rich reward, even when in quan- 

 tities which, if expressed in percentages, are almost inappreciable. 



The nature of the ore is also a factor of prime importance. 

 Some compounds yield the metals readily and cheaply, while 

 others, which in the case of the precious metals are often called 

 base ores, require complicated and it may be expensive metal- 

 lurgical treatment. The association of metals is likewise of 

 the highest importance. Copper or lead, for example, greatly 

 facilitate the extraction of gold and silver, whereas zinc in 

 large quantities is a hindrance. Conditions also change. An 

 ore which may have been valueless in early days may prove 

 a rich source of profit in later years and under improved condi- 

 tions. For instance, from 1870 for over twenty-five years 

 Bingham Canyon in Utah yielded lead-silver ores and minor 

 deposits of gold. It was known that in some mines low-grade 

 and base ores of copper and gold existed, but the fact was 

 carefully concealed and in at least one instance the shaft 

 into them was filled up, lest a general knowledge of the fact 

 should unfavorably affect the value of the property. To-day, 

 however, these ores are eagerly sought and their extraction 

 and treatment in thousands of tons daily are paying good 

 returns on very large capitalization. Another factor is the 

 expense of extraction. If simple and inexpensive methods 

 are possible, the area of profitable treatment is greatly widened. 

 Thus gold may need little else than a stream of water or even 

 a blast of air, whereas iron and copper require huge furnaces 

 and vast supplies of coke and fluxes. 



