448 
VOYAGE OF THE POTOMAC. [December, 
aie subject to them ; and the force of the shocks depends on the 
length of time that may have elapsed since the eruption preceding 
took place, in the neighbouring volcanoes. The cause of this 
energy in the shocks is supposed to be dependant on the thickness 
which the crust of cold and solid lava has obtained, and the re- 
sistance required to overcome it. 
One of the most remarkable earthquakes in Portugal, which 
took place in seventeen hundred and fifty-five, suddenly destroyed 
the city of Lisbon ; and in the course of six minutes crushed 
more than sixty thousand persons to death. The quay, con- 
structed of solid marble, sunk down into an enormous chasm, 
bearing with it all the crowd of people who had assembled upon 
it to save themselves from their falling houses. The sea now 
stands one hundred fathoms deep over this spot. - . 
There is no country on the surface of the globe more subject 
to earthquakes than South America, especially on its western 
coast, at the base of those gigantic mountains which extend 
through the country from north to south, and closely approximate 
the Pacific Ocean. Peru has been most frequently visited by 
these convulsions; and its capital, Lima, has been often shaken 
to its foundations. The great earthquake of seventeen hundred 
and forty-six entirely overturned that city, and crushed many of its 
inhabitants beneath the ruins of their houses. 
But the daring energy of man again rebuilt the city, which, al- 
though now better calculated to withstand the shocks of the un- 
dulating earth, is still frequently in part laid in ruins ; and the in- 
habitants rush from their homes, and seek refuge in the open plain, 
from their tottering tenements, which threaten to crush them be- 
neath their walls. 
It is surprising to observe how far the human mind can accus- 
tom itself to dangers, however imminent, and people can sleep 
with a feeling of security, when in a moment their dwellings may 
be tumbled in ruins over their heads, — their houses serving them 
for tombs. The people who dwell on the flanks of Vesuvius, 
Etna, or Teneriffe, have become so accustomed to volcanic phe- 
nomena, that they view them with little apprehension, although 
history, as well as their own observation and experience, shows 
them on what a treacherous soil they live : they still live on, ap- 
parently unmindful of their danger ; and when their houses are 
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