of vegetable origin.

(3.) In the atmosphere, which contains no less than 79 per cent.
of uncombined nitrogen.

In olden times ammonia was principally obtained from animal matter,
originally in Egypt by the distillation of camel dung, later on from
urine, and from the distillation of bones and horn. The quantity so
obtained was very small and the products very expensive. The
introduction of coal gas for illumination gave us a considerable and
constantly increasing supply of ammonia as a by-product of the gas
manufacture, and until recently all practical efforts to increase our
supply of ammonia were directed toward collecting and utilizing in the
best possible manner the ammonia so obtained. The immense extension of
the coal gas industry all over the world has in this way put us into
possession of a very considerable amount of sulphate of ammonia,
amounting in Europe now to 140,000 tons per annum. In recent years
this has been augmented by the ammonia obtained by the distillation of
shale, by the introduction of closed ovens for the manufacture of
coke, combined with apparatus for condensing the ammonia formed in
this manufacture, and also by the condensation of the ammonia
contained in the gases from blast furnaces working with coal. But all
these new sources have so far added only about 40,000 tons of
sulphate of ammonia to our supply, making a total of 180,000 tons per
annum, of which about 120,000 are produced in the United Kingdom,
while we still import 650,000 tons of nitrate of soda, equivalent to
500,000 tons of sulphate of ammonia, to make up our requirements.

Many processes have from time to time been proposed to obtain ammonia
from other sources. The distillation of turf, which contains upward of
3 per cent. of nitrogen, has received much attention, and a large
number of inventors have endeavored to produce ammonia from the
nitrogen of the air; but none of these processes has to my knowledge
been successful on a manufacturing scale.

My attention was called to this subject at an early part of my career.
Already, as far back as 1861, I undertook experiments to utilize, for
the production of ammonia, waste leather, a waste material of animal
origin at once abundant and very rich in nitrogen, containing from 12
per cent. to 15 per cent. of this element. Distillation in iron
retorts yielded about half the nitrogen of this material in the form
of ammonia, the carbon remaining in the retorts containing sti