one of the earth's ancient institutions.

Our geologists, who have unearthed many secrets not dreamed of even in
Humboldt's "good phylosopy," have settled the question of how the
different kinds of caves were formed, according to the character of
rocks they are in, or their location and depth, and the natural agencies
to whose action they show signs of having been subjected.

Dr. H.C. Hovey, in his "Celebrated American Caverns," says: "In visiting
caves of large extent, one is at first inclined to regard the long
halls, huge rifts, deep pits and lofty domes, as evidences of great
convulsions of nature, whereby the earth has been violently rent
asunder. But, while mechanical forces have had their share in the work,
as has been shown, the main agent in every case has been the
comparatively gentle, invisible gas known as carbonic acid. This is
generated by the decay of animal and vegetable substances, and is to a
considerable degree soluble in water. Under ordinary circumstances one
measure of water will absorb one measure of carbonic acid; and the eye
will detect no difference in its appearance. Under pressure the power of
absorption is rapidly increased, until the water thus surcharged has an
acid taste, and effervesces on flowing from the earth, as in Saratoga
water.

"Rain-water, falling amid leaves and grass, and sinking into the soil,
absorbs large quantities of carbonic acid. On reaching the underlying
limestone, the latter is instantly attacked by the acidulated water in
which it is dissolved and carried away.

"It is agreed among geologists, amazing as the statement may seem, that
the immense caverns of Virginia, Kentucky and Indiana, including Mammoth