emicians call the "sbalzo," or bounding into the air, to the height
of several yards, of masses slightly adhering to the surface. In some
towns a great part of the pavement stones were thrown up, and found
lying with their lower sides uppermost. In these cases, we must suppose
that they were propelled upwards by the momentum which they had
acquired; and that the adhesion of one end of the mass being greater
than that of the other, a rotatory motion had been communicated to them.
When the stone was projected to a sufficient height to perform somewhat
more than a quarter of a revolution in the air, it pitched down on its
edge, and fell with its lower side uppermost.

_Effects of earthquakes on the excavations of valleys._--The next class
of effects to be considered, are those more immediately connected with
the formation of valleys, in which the action of water was often
combined with that of the earthquake. The country agitated was composed,
as before stated, chiefly of argillaceous strata, intersected by deep
narrow valleys, sometimes from 500 to 600 feet deep. As the boundary
cliffs were in great part vertical, it will readily be conceived that,
amidst the various movements of the earth, the precipices overhanging
rivers, being without support on one side, were often thrown down. We
find, indeed, that inundations produced by obstructions in river-courses
are among the most disastrous consequences of great earthquakes in all
parts of the world, for the alluvial plains in the bottoms of valleys
are usually the most fertile and well-peopled parts of the whole
country; and whether the site of a town is above or below a temporary
barrier in the channel of a river, it is exposed to injury by the waters
either of a lake or flood.

_Landslips._--From each side of the deep valley or ravine of Terranuova
enormous masses of the adjoining flat country were detached, and cast
down into the course of the river, so as to give rise to great lakes.
Oaks, olive-trees, vineyards, and corn, were often seen growing at the
bottom of the ravine, as little injured as their former companions,
which still continued to flourish in the plain above, at least 500 feet
higher, and at the distance of about three-quarters of a mile. In one
part of this ravine was an enormous mass, 200 feet high and about 400
feet at its base, which had been detached by some former earthquake. It
is well attested, that this mass travelled down the ravine nearly four
m