and vinegar. The mineral called graphite or blacklead, is almost
pure carbon, and the diamond is but perfectly pure and crystal-
lized carbon. When united in certain proportions to oxygen, it then
loses its solid, assumes the gaseous form, and performs a most
important part in the process of vegetation. The compound thus
formed is called Carbonic acid, it extinguishes burning bodies, and
even in moderate proportion is fatal to animal life. Where com-
bustion does not take place from the presence of carbonic acid,
animal life cannot exist. It is the presence of this gas which
causes the impurity of air in wells, and hence the custom of letting
down a lighted candle before persons will venture to descend. If
the candle goes out the air is certainly impure, and persons cannot
encounter it with safety; and even when it exists in quantities not
sufficient to put out the candle, yet enough may be present to pro-
duce serious and even fatal effects to those who encounter it.
The injurious effects of this gas in wells can be obviated by pour-
ing into them a plentiful supply of quick-lime, in water.

Although when breathed it proves so noxious, yet when taken
into the system by other means, its effects are quite agreeable.

It is this which gives to the different artificial mineral waters
their pungency, and to ale, porter and some kinds of wine, their
pleasant flavor, which being lost by exposure to the air, renders
them stale, tasteless and flat. Water absorbs it readily, and thereby
acquires the ability of dissolving the mineral or inorganic constitu-
ents of soils; a most important property as we shall hereafter see.

It is always exhaled from the lungs of animals during respiration,
and is formed by the burning of wood and coal; it is emitted from
volcanoes, and is also a constant product of the decay of vegeta-
ble and animal matter, and therefore always exists in the atmosphere.

Since its sources are so constant and so abundant, the inquiry
naturally presents itself, how is it that it does not accumulate in
sufficient quantities to render the air unfit for the purpose of
breathing. Here the science of Chemistry unfolds at once the
Beneficence and Wisdom of the Creator in a most striking and
wonderful manner. This wisdom and goodness is moreover mani-
fested by means so perfect, and withal so simple as to call forth
our highest admiration of, and our greatest adoration and grati-
tude to Him who employs them for our good.

"Whenever it is vouchsafed to the feeble senses of man to cast
a glance into the depths of creation, he is compelled to acknow-
ledge the greatness and wisdom of the Creator of the world. The
greatest miracle which he is capable of comprehending, is that of
the infinite simplicity of the means, by the co-operation of which
order is preserved in the universe, as well as in organism, and the
life and continued existence of organized beings secured."

The causes which I have enumerated would, if not counteracted,

8