Januakt 5, 1906.1 



SCIENCE. 



19 



with the rocks, though not so striking a 

 one as in the ease of other metals. But the 

 great change necessary in aluminum is in 

 the method of combination. It is so tightly 

 locked up in silicates in the rocks as to pre- 

 ■clude direct extraction by any known 

 method. 



Nickel needs to be present in amounts 

 of several per cent., say two to five, and 

 occurs either alone or with copper. Cobalt 

 is always with it' in small amounts. 

 Platinum occurs in exceedingly small per- 

 centages. It is almost all obtained from 

 gravels in Russia, and the gravels yielded 

 in 1899, according to C. W. Purington, 

 about forty cents to the yard, platinum 

 being quoted in that year at $15 to $18' 

 per ounce. There was, therefore, in the- 

 gravels about one fortieth ounce in the- 

 yard, or one sixtieth in a ton or about; 

 5.5 hundred-thousandths of a per cent_ 

 Platinum in some rocks has been found in 

 amounts of one twentieth to one half 

 ounce, or from 16 hundred-thousandths 

 to 16 ten-thousandths of one per cent., but 

 they are rare and peculiar types. 



In order to be salable manganese ores of 

 themselves must yield about 50 per cent., 

 but if iron is also present they may be as 

 low as 40. Chromium has but one ore, and 

 it must contain about 40 per cent. Of 

 antimony, arsenic and cobalt it is hardly 

 possible to speak, since, except perhaps in 

 the case of the first, they are unimportant 

 by-products in the metallurgy of other ores. 



In summary it may be stated that in the 

 ores the metals must be present in amounts 

 shown in accompanying table. 



We now have before us some fundamen- 

 tal conceptions from which as a point of 

 departure we may set out upon the real dis- 

 cussion of the subject. We understand the 

 gross composition of the outer earth; we 

 have some idea of the quantitative distri- 

 bution of the metals in the rocks; especially 

 In the richer' instances; finally we have 



in Ores, 

 li-oft, 35-65 



Copper, 2-10 



Lead, 7-50 



Zinc, 25-60 



Silver, 1/12-1/150 



Percentage 

 Ounces to In the 



Ton. Earth's Crust, 



4.71 



.ooooi 



.OOOOi 

 .0000^ 

 2-25 .OOOOOOX 



Gold, 1/300-1/6,000 1/20-1 .OOOOOOOX 

 Tin, 1-3 .OOOX-.OOOOJ: 



Aiuininum, 30 8.13 



Nickel, 2-5 -01 



Manganese, 50 -O? 



Chromium, 40 .01 ■ 



seen the extent to whicli they must be con- 

 centrated ill order that they may be objects 

 of mining. The next step is to establish 

 first the agent or solvent which can effect 

 the collection of the sparsely distributed 

 metals, and second the places where the 

 precipitation of them takes place. We may 

 then inquire more particularly into the 

 source of the agent and the methods of it's 

 operation. In order to do this in the time 

 at command I must remorselessly focus at- 

 tention on the large and essential features, 

 resolutely avoiding every side issue or 

 minor point, however inviting. 



The one solvent which is sufficiently 

 abundant is water, and practically all ob- 

 servers are agreed that for the vast ma- 

 jority of ore deposits it has been the vehicle 

 of concentration. Of course it need not 

 operate alone. On the contrary, easily 

 dissolved and ever-present materials like 

 alkalies may, and undoubtedly do, increase 

 its efficiency. It does not operate neces- 

 sarily as cold water. On the contrary, we 

 all know that the earth grows hotter as we 

 go down, so that descending waters could 

 not go far without feeling this influence. 

 Volcanoes, too, indicate to us that there are 

 localities where heat is developed in enor- 

 mous amounts and not far below the sur- 

 face. There is, therefore, no lack of heat ■ 

 and we only ijeed to-^be familiar with the 

 western country to know that there is no 

 lack of hot springs when we take a compre- 



