ed the recovered land spread
themselves out in numerous fresh-water lakes, which stood an hundred
and fifty feet higher than the present bed of the Tiber. In these
lakes were formed two kinds of fresh-water strata--the first composed
of sand and marl; and the second, where mineral springs gushed forth
through the volcanic rock, of travertine--a peculiar reddish-brown or
yellow calcareous rock, of which St. Peter's and many of the buildings
of modern Rome are composed. We find lacustrine marls on the sides of
the Esquiline Hill where it slopes down into the Forum, and
fresh-water bivalve and univalve shells in the ground under the
equestrian statue of Marcus Aurelius on the Capitol; while on the face
of the Aventine Hill, overhanging the Tiber at a height of ninety
feet, is a cliff of travertine, which is half a mile long. The lakes
which formed these deposits must have covered their sites for many
ages. At last, by some new change of level, the lakes retired, and the
Tiber scooped out for itself its present channel to the sea.

When man came upon the scene we have no definite information; but
numerous flints and stone-weapons have been found among the black
pumice breccias of the Campagna mixed with remains of the primitive
bison, the elephant, and the rhinoceros. Human eyes must therefore
have gazed upon the volcanoes of the Roman plain. Human beings,
occupying the outposts of the Sabine Hills, must have seen that plain
broken up by the sea into a complicated archipelago, and beheld in the
very act of formation that wonderful region destined long ages
afterwards to be the scene of some of the greatest events in human
history. The Alban Hills, whose present quiet beauty, adorned with
white gem-like towns, and softened with the purple hues of heaven,
strikes every visitor with admiration, were active volcanoes pouring
streams of lava down into the plain even after the foundation of the
Eternal City. Livy mentions that under the third king of Rome, a
shower of stones, accompanied by a loud noise, was thrown up from the
Alban Mount--a prodigy which gave rise to a nine days' festival
annually celebrated long after by the people of Latium. The remarkable
funereal urns found buried under a bed of volcanic matter between
Marino and Castel Gandolfo on the Alban Hills are an incontrovertible
proof that showers of volcanic ashes must have been ejected from the
neighbouring volcano when the country was inhabited by human beings;