1878.] Economy of Nitrogen. 163 
Leather-waste will lie for years in the soil undecomposed, 
and appears to exert no appreciable fertilising influence. 
Hence a non-nitrogenous substitute for leather would be a 
boon of no small magnitude to the world. 
We have thus given a catalogue, by no means exhaustive, 
of the operations and processes, industrial and domestic, by 
which nitrogen is wasted. This waste, as we have seen, 
turns mainly on its transformation from the combined or 
solidified state to the free or gaseous condition as it is found 
in the atmosphere. But in this state, we shall be asked, is 
it not plentiful, almost to infinity, and does there not exist 
here one of those beautiful processes of circulation, of 
which we often read, by which it is restored to the combined 
or solidified state, and made again available ? Yes, the 
store of atmospheric nitrogen is all but infinite, and we dare 
not assert that there is absolutely no natural process by 
which it can be re-combined with other elements ; but these 
processes are slow in their operation, and, as far as we can 
judge, they cannot keep pace with our waste. They do not 
build up as quickly as we can destroy. We know that the 
atmosphere contains traces of ammonia, and that nitric acid 
in small quantity may be detected in rain, especially that 
• which accompanies a thunderstorm; but we are still doubt- 
ful how much of this combined nitrogen has been really 
formed at the expense of the inert atmospheric nitrogen, 
and how much, on the other hand, is merely the decomposi- 
tion of organic matter upon the earth’s surface. It is 
ascertained that the elebtric spark, i.e., lightning, on passing 
through a mixture of oxygen and nitrogen, — in other words, 
through common air, — effects the combination of these two 
elements so as to form nitric acid. Water holding in solu- 
tion atmospheric air, as do all normal waters on the earth’s 
surface, is found to yield nitric acid at the positive pole of 
the battery and ammonia at the negative. Hydrogen and 
nitrogen are also, according to the researches of Donkin, 
induced to combine by the adlion of the effluve, or silent 
eledtric discharge. But all such processes, however varied, 
have been found to be exceedingly slow in their abtion, and 
hence incapable of practical application in the arts. Ozone 
was once appealed to in every difficulty, but it has been 
proved incapable of oxidising free nitrogen to nitric acid in 
presence of water, as was suggested. Other reactions have 
been proposed, but none of them has proved distinctly and 
unequivocally successful as a means of combining the free 
nitrogen of the air into ammonia, or nitric acid, or cyano- 
gen, or any other available compound. To solve this, the 
