the formation of valleys--Concluding remarks.

_Calabria_, 1783.--Of the numerous earthquakes which have occurred in
different parts of the globe, during the last 100 years, that of
Calabria, in 1783, is almost the only one of which the geologist can be
said to have such a circumstantial account as to enable him fully to
appreciate the changes which this cause is capable of producing in the
lapse of ages. The shocks began in February, 1783, and lasted for nearly
four years, to the end of 1786. Neither in duration, nor in violence,
nor in the extent of territory moved, was this convulsion remarkable,
when contrasted with many experienced in other countries, both during
the last and present century; nor were the alterations which it
occasioned in the relative level of hill and valley, land and sea, so
great as those effected by some subterranean movements in South America,
in later times. The importance of the earthquake in question arises from
the circumstance, that Calabria is the only spot hitherto visited, both
during and after the convulsions, by men possessing sufficient leisure,
zeal, and scientific information, to enable them to collect and describe
with accuracy the physical facts which throw light on geological
questions.

[Illustration: Fig. 42.]

_Authorities._--Among the numerous authorities, Vivenzio, physician to
the king of Naples, transmitted to the court a regular statement of his
observations during the continuance of the shocks; and his narrative is
drawn up with care and clearness.[663] Francesco Antonio Grimaldi, then
secretary of war, visited the different provinces at the king's command,
and published a most detailed description of the permanent changes in
the surface.[664] He measured the length, breadth, and depth of the
different fissures and gulfs which opened, and ascertained their number
in many provinces. His comments, moreover, on the reports of the
inhabitants, and his explanations of their relations, are judicious and
instructive. Pignataro, a physician residing at Monteleone, a town
placed in the very centre of the convulsions, kept a register of the
shocks, distinguishing them into four classes, according to their degree
of violence. From his work, it appears that, in the year 1783, the
number was 949, of which 501 were shocks of the first degree of force;
and in the following year there were 151, of which 98 were of the first
magnitude.

Count Ippolito, also, and many others