The Encyclopedia of Geography [pp. 307-313]

1q43.) The Encyc?opdia of Geography. 307
THE ENCYCLOPLEDIA OF GEOGRAPHY.
including every slighter agitation, earthquakes appear to be exceedingly numerous, and it may be
maintained that not a week passes in which the
earth's surface in some place or other is not more
or less agitated. The great number of concussions observed in civilized countries, and the fact
that some districts are c o nstantly agitated by them,
entitle us to draw the conclusion. Their return in
the places most subject to the m, and in the place s
cohere they are less frequent, is not regulated by
any prewise period of time. Their appearance is
not connected with any particula r s eason o f the
year or state of the atmosphere, and they take place
by day as well as by night.
" Phenomena of earlhqu,akes. The phenomena
peculiar to earthquakes are in themselves sufficiently simple. They consist in tremblings and
oscillations of the earth's surface, called shocks;
extending over greater or smaller tracts of country,
and frequently following a particular direction.
The shocks appear at first chiefly as perpendicular
heavings; then as horizontal undulations or oscillatioIn; lastly, in some instances, there is a violent agitation: the motion is more or less rotatory.
If to these we add the rending, slipping, rising and
sinking of the ground, the violent agitations of
the sea, lakes, rivers and springs; consisting, in
springs, in their drying up or bursting forth with
great violence; in lakes, rivers, and the ocean,
in their falling and rising, and rushing backwards
and forwards, owing to the sinking and rising of
the land, we obtain an enumeration of the principal phenomena. As the subject is very interesting, we shall view it somewhat in detail, and
under the following heads: 1. Shocks. 2. Extent
of earthquakes. 3. Duration of shocks. 4. Magnitude of rents formed, and the phenomena connected with them. 5. Elevation and subsidence of
the land. 6. Agitations in the sea. 7. Notice of
particular earthquakes.
" 1. Shocks. The slightest shocks of an earthquake, consisting of perpendicular heavings and
horizontal undulations, commonly produce rents in
houses, moving light objects in them, as articles of
furniture. Persons unacquainted with the phenomenon, or who do not perceive it from the subterraneous noise resembling thunder which accoanpanies it, feel unsteady while in their beds, but particularly when sitting, and believe themselves seized
with a sudden giddiness. The shocks proceed
gradually to be more violent, and then they are
very easily perceived even by the inexperienced.
Then the most substantial buildings are shattered
to pieces, and the inhabitants buried beneath their
rulins: while buildings of a lighter construction are
only rent, and vtery slender reed hults are least of
all exposed to destruction. In some cases the
fracturing, or as it were trituration, surpasses description. Hence, for the plainest reasons, it is
most dangerous to remain n houses or inhabited
PHILADELPHIA: LEA AND BLANCHARD.
Wre noticed the first part of this publication in
a former No. It has reached Part III-on better
paper and larger type, than the New-York publications. This also is a very valuable, cheap and
useful work-for 25 cents the No. Formerly,
Philadelphia was the great mart for books. But
New-York, with her greedy appetite that is swallowing up every thing, has stretched forth her
hands, through the Messrs. Harper, after this branch
of trade also. We are glad to see the well-known
and enterprising publishers of Philadelphia, disputing the palm of cheap literature with her rival sister, New-York. Messrs. Lea & Blanchard could
not have been more fortunate in their selection of
a work, than they have been in that of this Encyclopadia. We have not space at present for more
than one extract-intending to make others from
future No's. And, as earthquakes have been rife
of late-we will let Murray's Geographical Encyelopeedia speak for itself on that subject:
" On earthquakes, and the changes they produce
on the earth's surface. Werner distinguishes two
kinds of earthquakes. Some, he says, appear to
be connected with a particular volcano, and to have
their focus in the same region as it. They are
only felt to the distance of a few leagues around,
and their paroxysms are almost always connected
with those of the volcano. Others, which appear
to have their focus at a much greater depth, and
whose effects are much greater, are propagated to
immense distances with incredible celerity, and are
felt almost at the same time at points thousands of
miles distant from each other. Some of the latter,
however, approach the former, and are still connected with volcanic phenomena. Thus, during
the earthquake which overturned Lima in 1746,
and which was one of the most terrible that has
been recorded, four volcanoes opened in one night,
and the agitation of the earth ceased.
" U7:dversality of earthquakes. If in the more
violent we include the slighter agitations of the
earth's surface in particular places, earthquakes
may be said to be universal or general, and we
may affirm that no considerable country is entirely
exempted from them. Sandy deserts and fertile
regions, primitive, secondary, and tertiary hills,
extensive plains, and even marshy districts but little elevated above the level of the sea, afford no
protection against these destructive phenomena,
which are equally prevalent in cold, in temperate,
and in tropical climates. They are, however,
generally considered more fiequent near to coasts;
thus Syria, the coasts and islands of Asia, America, the European coasts of the Mediterranean,
and Iceland, are most subject to them; while the
plains of Africa, Asia and the North of Europe
are least exposed. Viewing the whole earth, and
1843.1
The Encyclop6edia of Geogi-aphy.
307