Since then the industry has developed with amazing rapidity until in
1913 the United States produced over three million tons of phosphates,
nearly half of which was sent abroad. The chief source at present is the
Florida pebbles, which are dredged up from the bottoms of lakes and
rivers or washed out from the banks of streams by a hydraulic jet. The
gravel is washed free from the sand and clay, screened and dried, and
then is ready for shipment. The rock deposits of Florida and South
Carolina are more limited than the pebble beds and may be exhausted in
twenty-five or thirty years, but Tennessee and Kentucky have a lot in
reserve and behind them are Idaho, Wyoming and other western states with
millions of acres of phosphate land, so in this respect we are
independent.

But even here the war hit us hard. For the calcium phosphate as it comes
from the ground is not altogether available because it is not very
soluble and the plants can only use what they can get in the water that
they suck up from the soil. But if the phosphate is treated with
sulfuric acid it becomes more soluble and this product is sold as
"superphosphate." The sulfuric acid is made mostly from iron pyrite and
this we have been content to import, over 800,000 tons of it a year,
largely from Spain, although we have an abundance at home. Since the
shortage of shipping shut off the foreign supply we are using more of
our own pyrite and also our deposits of native sulfur along the Gulf
coast. But as a consequence of this sulfuric acid during the war went up
from $5 to $25 a ton and acidulated phosphates rose correspondingly.

Germany is short on natural phosphates as she is long on natural potash.
But she has made up for it by utilizing a by-product of her steelworks.
When phosphorus occurs in iron ore, even in minute amounts, it makes the
steel brittle. Much of the iron ores of Alsace-Lorraine were formerly