188 THE PROBLEM OF THE METALLIFEROUS VEINS. 



properties of the latter but the slightest suggestion of their presence. 

 Chance discoveries must have first revealed the possibilities of pro- 

 ducing iron from its ore — really a ver}^ simple process when small 

 quantities are involved, — of making bronze from the ores of copper 

 and tin, of making brass with the ores of copper and zinc, of reduc- 

 ing copper and lead from their natural compounds, and of freeing 

 silver from its chief associate, lead. All of these processes were 

 extensively practiced under the Chinese, Phoenicians, Greeks, Romans, 

 and other ancient peoples. 



As the need of weapons in war, the advantages of metallic currency, 

 and the want of household utensils became felt, and as the minerals 

 Avhich yield the metals became recognized as such, the art of mining 

 grew to be something more than the digging and washing of gravels, 

 and in the long course of time developed into its present stage — as 

 one of the most difficult branches of engineering. Chemistry raised 

 metallurgical processes from the art of obtaining some of a metal 

 from its ore to the art of obtaining almost all of it and of accounting 

 for what escaped. It is, in fact, in this scientifie accounting for 

 everything that modern processes chiefly diifer from those of the 

 ancients. 



Of all the metals the most important which minister to the needs 

 of daily life are the following, ranged as nearly as possible in the 

 order of their usefulness: Iron, copper, lead, zinc, silver, gold, tin, 

 aluminum, nickel, platinum, manganese, chromium, quicksilver, anti- 

 mony, arsenic, and cobalt. The others are of very minor importance, 

 although often indispensable for certain restricted uses. 



The manner of occurrence of these metals in the earth and their 

 amounts in ores which admit of practicable working are fundamental 

 facts in all our industrial development, and some accurate knowledge 

 of them ought to be a part of the intellectual equipment of every well- 

 educated man. The matter may well appeal to Americans, since the 

 United States has developed within a few years into the foremost 

 producer of iron, copper, lead, coal, and, until recent years, of gold 

 and silver ; but, with regard to gold, they have of late alternated in 

 the leadership with the Transvaal and Australia, and in silver are 

 now second to Mexico. 



Despite the enormous product of foodstuffs, American mining 

 develoi^ments are of the same order of magnitude, and the mineral 

 resources of the country have proved to be one of the richest posses- 

 sions of Its people. 



We may best gain a proper conception of the problem of the metal- 

 liferous veins if we state at the outset the gross composition of the 

 outer portion of the globe, so far as geologists have been able to 

 express it by grouping analyses of rocks. We may then note among 

 the elements mentioned such of the metals as have just been cited, 



