a final result, a pure and beautiful prismatic saltpetre, most
economically and abundantly.

Instead of working on a hundred pounds of earth to obtain at most eight
or nine pounds of saltpetre, a hundred pounds of soda saltpetre will
afford more than one hundred and nine pounds of potash saltpetre, when
skilfully treated. Here, then, we have, by simple chemical treatment
of an imported, but very cheap salt, a result constituting a source of
abundant supply of potash saltpetre, _without the loss of the agent_
concerned in the transformation.

We have traced slightly in outline the formation of saltpetre to the
action of ozonized oxygen on nitrogen compounds, in the atmosphere, or
in the earth,--the conditions being the same in both cases. If we pursue
the study of this action of ozonized oxygen farther, we shall not
restrict its combining disposition to these compounds, but prove that it
has the power of uniting directly with the nitrogen naturally forming
part of the pure air. While nitrogenized bodies are present, however,
in the atmosphere, or in the humid artificial heaps of saltpetre
plantations, the action of ozonized oxygen is on these, and the nitrous
compounds formed unite with the bases lime, soda, and potash, also
present, to form saltpetre.

Under all the conditions necessary, we see the permanent gases, oxygen
and nitrogen, leaving the atmosphere and changing from their gaseous to
a solid dry state, when they become chemically combined with potash, and
there are 53-46/100 parts of the gaseous matter and 46-54/100 parts of
the potash in 100 parts of the saltpetre by weight.

Having now found what saltpetre is and how it is formed, let us advance
to the consideration of it as a source of power.

Through the exertion of chemical attraction the gaseous elements of the
atmosphere have become solid in the saltpetre; and as we know the weight
of this part in a cubic inch of saltpetre, the volume of the gases
combined is easily ascertained to be about eight hundred times that of
the saltpetre. Hence, as every cubic inch of condensation represents
an atmosphere as large as the cubic inch of saltpetre formed, we may
roughly estimate that the condensing force arising from chemical
attraction in this case is 800 times 15 lbs., or 12,000 lbs.!

Strictly speaking, only about four-tenths of a cubic inch of potash
holds this enormous power in connection with it so as to form a cubic
inch of saltpetre, which we may han