Januaby 5, 1906.] 



SCIENCE. 



15 



of the Lake Superior mines; iron in an 

 occasional meteorite, whicli, if its fall had 

 been observed, was considered to be the 

 image of a god, descended from the skies f 

 silver in occasional nuggets with the more 

 common ones of gold; and possibly a rare 

 bit of platinum. Besides these no other 

 metal can have been known, because all the 

 rest and all of those mentioned, when 

 locked up in their ores, give in the physical 

 properties of the latter but the slightest 

 suggestion of their presence. Chance dis- 

 coveries must have first revealed the pos- 

 sibilities of producing iron from its ore— 

 really a very 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 

 reducing copper and lead from their nat- 

 ural compounds ; and of freeing silver from 

 its chief associate, lead. All of these proc- 

 esses were extensively practised under the 

 Chinese, Phenicians, Greeks, Romans and 

 other ancient peoples. 



As l^he need of weapons in war, the ad- 

 vantages of metallic currency and the want 

 of household utensils became felt, and as the 

 minerals which 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 engi- 

 neering. 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 scientific 

 accounting for everything, that modern 

 processes chiefly differ 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 pos- 



= As in the ease of Diana of the Ephesians and 

 the deity of the Carthaginians. 



sible in the order of their usefulness: 

 Iron, copper, lead, zinc, silver, gold, tin, 

 aluminum, nickel, platinum, manganese, 

 chromium, quicksilver, antimony, 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 de- 

 velopment, 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 have developed 

 within a few years into the foremost pro- 

 ducers 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 food- 

 stuffs, American mining developments are 

 of the same of-der of magnitude; and the 

 mineral resources of the country have 

 proved to be one of the richest possessions 

 of its people. 



We may best gain a proper conception of 

 the problem of the metalliferous 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 and 

 may remark the rarity of the others; we 

 may next set forth the necessary percent- 

 ages of each metal which make a deposit 

 an ore, that is, make it rich enough for 

 profitable working. By comparison we 

 can grasp in a general way the amount of 

 concentration which must be accomplished 

 by the geological agents in order to collect 

 from a naturally lean distribution in rocks 



