the discovery of the nitrogen-fixing bacteria, the custom
prevailed of sowing pea-like plants every third year and then plowing
them under to enrich the soil. But such local supplies were always
inadequate and as soon as deposits of fertilizers were discovered
anywhere in the world they were drawn upon. The richest of these was the
Chincha Islands off the coast of Peru, where millions of penguins and
pelicans had lived in a most untidy manner for untold centuries. The
guano composed of the excrement of the birds mixed with the remains of
dead birds and the fishes they fed upon was piled up to a depth of 120
feet. From this Isle of Penguins--which is not that described by Anatole
France--a billion dollars' worth of guano was taken and the deposit was
soon exhausted.

Then the attention of the world was directed to the mainland of Peru and
Chile, where similar guano deposits had been accumulated and, not being
washed away on account of the lack of rain, had been deposited as sodium
nitrate, or "saltpeter." These beds were discovered by a German, Taddeo
Haenke, in 1809, but it was not until the last quarter of the century
that the nitrates came into common use as a fertilizer. Since then more
than 53,000,000 tons have been taken out of these beds and the
exportation has risen to a rate of 2,500,000 to 3,000,000 tons a year.
How much longer they will last is a matter of opinion and opinion is
largely influenced by whether you have your money invested in Chilean
nitrate stock or in one of the new synthetic processes for making
nitrates. The United States Department of Agriculture says the nitrate
beds will be exhausted in a few years. On the other hand the Chilean
Inspector General of Nitrate Deposits in his latest official report says
that they will last for two hundred years at the present rate and that
then there are incalculable areas of low grade deposits, containing less
than eleven per cent., to be drawn upon.

Anyhow, the South American beds cannot long supply the world's need of
nitrates and we shall some time be starving unless creative chemistry
comes to the rescue. In 1898 Sir William Crookes--the discoverer of the
"Crookes tubes," the radiometer and radiant matter--startled the British
Association for the Advancement of Science by declaring that the world
was nearing the limit of wheat production and that by 1931 the
bread-eaters, the Caucasians, would have to turn to other grains or
restrict their population w