NATURAL. EESOUECES — LITTLE. 233 
1916. The demand for copper by the Central Powers caused roofs 
to be stripped and brass and bronze articles of use or ornament to be 
everywhere commandeered. Our own position in regard to copper 
may be summed up in the statement that the Americas yield 75 per 
cent of the world's output and the United States almost 60 per cent. 
We have in the flotation process as applied to copper production 
another good example of a new industrial method, due to research, 
which in the nick of time permitted a vast expansion in the output 
of an essential metal. 
Zinc, which finds a great use in brass, composed normally of two- 
thirds copper and one-third zinc, enters obviously into the constitu- 
tion of a vast variety of military supplies. The demand for zinc led 
to an orgy of zinc smelting because most of the world's smelters 
outside of Germany and the United States stood along the Meuse 
Eiver in direct line of the German advance. As to this metal 
Germany was favorably placed, since one of the greatest zinc fields 
in the world is in Silesia. The Allies, however, suffered immense 
losses of brass during their retreat early in 1918, and toward the 
end of the war the United States became practically their sole 
source of supply. The shortage of copper in Germany led in that 
country to the substitution therefor of various alloys of zinc. 
Lead is one of our most useful metals and has been identified with 
military operations since the arquebus replaced the crossbow. It is 
almost indispensable for pipe, solder, bearing metals, terne-plate, 
small arms, bullets, shrapnel, and functions with perhaps equal 
effectiveness in the type so essential to propaganda. The United 
States has always imported much lead ore from Mexico. The supply 
was short in 1917, but increasingly stable conditions in that country 
enabled her to send us almost as much lead in the first half of 1918 
as we imported from all countries in the previous year. 
For many uses antimony is closely associated with lead by reason 
of the greatly increased hardness of antimony-lead alloys. Anti- 
mony, therefore, also finds extensive use in the type foundry and is 
a common constituent of bearing metals. 
Reference has already been made to the ubiquity of the indispen- 
sable tin can, and the shortage of tin was the cause of almost as much 
anxiety as that of platinum, the world's output of 140,000 tons being 
inadequate to meet the demand. We ordinarily consume 70 per 
cent of the world's supply, to which we contribute practically 
nothing. Tin finds important use as a constituent of solders, in 
which, however, it may, if necessary, be replaced by cadmium, and 
some cadmium was used in France as a deoxidizer in bronze for tele- 
phone and telegraph equipment. 
Aluminum is one of the most important and interesting of all 
the war metals, and its whole history is replete with peculiar interest. 
