lloons filled with miasmatic air. 'These
considerations,' says M. Schoenbein, 'shew us how little the miasma of
the air are to be appreciated by weight, even when they exist therein
in a quantity very sensible to the smell, and how small is the
proportion of ozone necessary to destroy the miasm produced by the
putrefaction of organic substances, and diffused through the
atmosphere.'

The presence of ozone in any vessel or in the atmosphere, may be
detected by a test-paper which has been moistened with a solution
composed of 1 part of pure iodide of potassium, 10 parts of starch,
and 100 parts of water, boiled together for a few moments. Paper so
prepared turns immediately blue when exposed to the action of ozone,
the tint being lighter or darker according to the quantity.
Schoenbein's ozonometer consists of 750 slips of dry bibulous paper
prepared in the manner described; and with a scale of tints and
instructions, sufficient to make observations on the ozone of the
atmosphere twice a day for a year. After exposure to the ozone, they
require to be moistened to bring out the colour.

M. Schoenbein continues: 'We must admit that the electric discharges
which take place incessantly in different parts of the atmosphere, and
causing therein a formation of ozone, purify the air by this means of
organic, or, more generally, oxidizable miasma; and that they have
thus the important office of maintaining it in a state of purity
suitable to animal life. By means of atmospheric electricity, and,
indirectly, nature thus attains on a great scale the object that we
sometimes seek to accomplish in a limited space by fumigations with
chlorine.

'Here, as in many other cases, we see nature effecting two different
objects at one stroke. For if the oxidizable miasma are destroyed by
atmospheric ozone, they, in turn, cause the latter to disappear, and
we have seen that it is itself a miasm. This is doubtless the reason
why ozone does not accumulate in the atmosphere in greater proportion
than the oxidizable miasma, notwithstanding the constant formation of
one and the other.

'In all times, the idea has been held, that storms purify the air, and
I do not think that this opinion is ill-founded. We know, in fact,
that storms give rise to a more abundant production of ozone. It is
possible, and even probable, that sometimes, in particular localities,
there may not be a just relation between the ozone and the oxidizable
miasma in the air,