ts upon its surface,
either or both of them, the oxygen, being specifically heavier than the
nitrogen or hydrogen, would settle immediately upon the earth, and,
coming in contact with fires here and there, its whole surface would, in
an instant of time, be enveloped in one general conflagration, and "the
day of the Lord," spoken of in the Scriptures, "in which the heavens
shall pass away with a great noise, and the elements shall melt with
fervent heat, the earth also, and the things therein shall be burned
up," would be speedily ushered in. He who understands the first
principles of chemical science can not fail to perceive how readily (and
in perfect accordance with laws well understood) such a general
conflagration would take place were the great Architect simply to
resolve these two elements--air and water--into their constituent parts.
How full of meaning to such a one are the words of the Psalmist, _The
heavens declare the glory of God, and the firmament showeth his
handiwork_.

One more illustration must suffice. All fluids, except water, contract
in volume as they become colder to the point of congelation. But the
point of greatest density in water is about eight degrees above
freezing. As the temperature of ALL fluids _increases_ above this point,
their volume increases. As the temperature of all fluids, with the
single exception of WATER, _decreases_, the volume decreases down to the
freezing point. Water increases in density as it becomes colder until it
reaches the temperature of forty degrees--eight degrees above the
freezing point--when it begins to expand. This only exception to the
general law of fluids is of greater importance in the economy of nature
than most persons are conscious of. As the cold season advances in the
temperate and frigid zones, the water in our lakes and rivers is reduced
to the temperature of forty degrees; but at this point, by a beneficent
provision of an All-wise Providence, the upper substratum becomes
specifically lighter, and is converted into a covering of ice, which,
resting upon the water beneath, protects it from freezing. Moreover,
when water is converted into ice, one hundred and forty degrees of heat
are given out, a part of which, entering into the water below, retards
the further formation of ice.[54]

[54] I may here add, that exactly the _reverse_ is true in the _melting_
of snow and ice. It requires as much heat to convert these solids into
fluids, witho