nce, and even named
"ozone." Among the new characters thus conferred on it is the power of
uniting with or burning many substances. This ozonized oxygen, when
brought into mixture with many nitrogenized bodies, forms with them
nitrous acids, completely destroying their former condition and
composition; hence, in the atmosphere, this part of the oxygen becomes
a purifier of the whole mass, from which it removes putrescent
exhalations, miasmatic vapors, and the effluvia from every source of sea
or land. Very curious are the effects of this active oxygen, which is
ever present in some portion of the atmosphere. Moved by the wind, mixed
with the impure upward currents rising from cities, it seizes on
and changes rapidly all foulness, and if the currents are not too
voluminous, the impure air becomes changed to pure. As ozonized oxygen
can be easily detected, we may pass from the city, where (overpowered
by the exhalations) it does not exist, and find it in the air of the
vicinity; and moving away several miles, ascertain that a normal amount
there prevails, and that step by step, on our return to abodes of a
dense population, the quantity diminishes and finally all disappears.

We are now prepared to answer the second part of the question which was
suggested, and to find that nitrous acids formed in the atmosphere
by direct oxidation of nitrogenous matter may unite with the ammonia
present to produce one kind of saltpetre; and when the rains or the dews
carry this to the earth, the salts of lime, potash, and soda there found
will decompose this ammoniacal saltpetre, and set the ammonia free, to
act over again its part. So in regard to decomposing organic matters in
the soil: ozonized oxygen changes them in the same way. The earth
and calcareous rocks of caves, penetrated by the air, slowly produce
saltpetre, and before the theory of the action was understood,
artificial imitation of natural conditions enabled us to manufacture
saltpetre. Animal remains, stratified with porous earth or the sweepings
of cities, and disposed in long heaps or walls, protected from rain, but
exposed to the prevailing winds, soon form nitrous salts, and a large
space covered with these deposits carefully tended forms a saltpetre
plantation. France, Prussia, Sweden, Switzerland, and other countries,
have been supplied with saltpetre from similar artificial arrangements.

But the atmosphere is washed most thoroughly by the rains falling in and
nea