All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

Living on the Air 271 be achieved. The staple element—nitrogen—was immediately to hand. Seeing that it forms four- fifths of the air we breathe, there was not likely to be a dearth of this material, while it was never likely to become expensive to acquire. It is computed that there are some 4,000,000,000,000,000,000 tons of this staple constituent enveloping our earth. What an enormous reservoir upon which to draw for supplies ! But this nitrogen is “ free.” That is to say, it is not combined with the oxygen. It requires to be caught, or, as it is termed, “ fixed,” so that it may be administered to the plant in the form which it is able to assimilate, and through the roots. Fortu- nately, the means for consummating this end are as readily available as the raw gas itself. It was only necessary to reproduce in a factory what Nature is doing every minute of the day throughout the world where vegetable life exists. Nature fixes the nitrogen in a very simple manner. A flash of lightning, which is but an electric spark upon a gigantic scale, such as Cavendish employed, burns the air, causing the nitrogen to combine with the oxygen. This oxida- tion process produces nitric oxide. But the fumes, instead of poisoning us, become converted into nitric acid by the falling rain. This acid is brought to earth and, percolating through the soil, enters into combination with the latter, thereby forming the nitrate upon which the plant can feed. Nature’s process sounds extremely simple, as, indeed, it is, but it did not prove such a simple matter to reproduce this action in a controlled manner for the factory. Many an inventor attempted to use the electric spark upon an extensive scale to burn