in combination with some other elements in the form of food or
fertilizer so we can make use of it as we set it free. Fixed nitrogen in
its cheapest form, Chile saltpeter, rose to $250 during the war. Free
nitrogen costs nothing and is good for nothing. If a land-owner has a
right to an expanding pyramid of air above him to the limits of the
atmosphere--as, I believe, the courts have decided in the eaves-dropping
cases--then for every square foot of his ground he owns as much
nitrogen as he could buy for $2500. The air is four-fifths free nitrogen
and if we could absorb it in our lungs as we do the oxygen of the other
fifth a few minutes breathing would give us a full meal. But we let this
free nitrogen all out again through our noses and then go and pay 35
cents a pound for steak or 60 cents a dozen for eggs in order to get
enough combined nitrogen to live on. Though man is immersed in an ocean
of nitrogen, yet he cannot make use of it. He is like Coleridge's
"Ancient Mariner" with "water, water, everywhere, nor any drop to
drink."

Nitrogen is, as Hood said not so truly about gold, "hard to get and hard
to hold." The bacteria that form the nodules on the roots of peas and
beans have the power that man has not of utilizing free nitrogen.
Instead of this quiet inconspicuous process man has to call upon the
lightning when he wants to fix nitrogen. The air contains the oxygen and
nitrogen which it is desired to combine to form nitrates but the atoms
are paired, like to like. Passing an electric spark through the air
breaks up some of these pairs and in the confusion of the shock the
lonely atoms seize on their nearest neighbor and so may get partners of
the other sort. I have seen this same thing happen in a square dance
where somebody made a blunder. It is easy to understand the reaction if
we represent the atoms of oxygen and nitrogen by the initials of their
names in this fashion: