The morning call., 1891-09-12
THE SALVADOR EARTHQUAKE.

1t will probably prove that the stories
which have reached US regarding Wednes-
days earthquake at Salvador are exagger-
ated. There is always disposition to over
state the damage done by such catastrophes.
But there appears TO be no doubt that the
little republic has had a pretty thorough
shaking up.
Salvador is to the manner born. Four
times, since the historical period began, has
the capital city been destroyed by earth
quakes, and the survivors among the people
have been forced to rebuild; the last de-
structive esrthq lake was in 1854. But the
earth is always quaking there. traveller
who visited the State in 1879 counted 600
shocks in the course of ten days. Back of
the city, in the mountains. are a score or
more of volcanoes. some OF which are con-
stantly, while others are internationally,
active. The natives believe that these vol
canoes act as safety-valves for the subter-
Tanean forces. But careful study of seis-
mic phenomena does not sustain the theory
that volcanic eruptiOns obviate earthquakes.
On the contrary the two sets Of phenomena
are often simultaneous and apparently
caused by the same agency. The Gala
brian earthquakes which involved heavy
loss of life were accompanied by periodic
eruptions from Vesuvius
Seismology is 50 young a science that it is
more fruitful Of conjecture than anything
else. Nobody knows the cause Of earth
quakes; every theory which has been ad-
vanced to account for them is open TO objec-
tions which seem fatal. It is certain that
they are most frequent in our day within
the limits Of a belt between about $50 north
and 150 north. But there was an earthquake
a few years ago in Chile in 30o south, which
raised the whole littoTal several feet; Hecla
is in Go north; Lisbon is near the line of 400
north, and on the same meridian lies that
range Of country in Asia Minor and Syria
which was devastated by earthquakes Just
before and at the beginning of the historic
period. It was supposed that the United
States was free from destructive earth
quakes until the catastrophe at Charleston
in 1886. That occurrence required reyis-
ion of current theories. 1t appears that you
find earthquakes as the miners say you find
gold, where they happen to occur.
A theory which has gained adherents of
late years is that all or nearly all earth
quakes are of submarine origin. The idea
was suggested by the fact that the phe-
nomena never occurred far from the sea-
board, and it was confirmed by study of the
tidal waves which accompanied the earth
quake at Lisbon In 1855, and that which de-
stroyed africa in 1868. The tidal wave at
Lisbon was sixty feet in height, and swept
in from the Atlantic from some seismic
focus perhaps far out at sea- No survey Of
the bottom of the sea has yet enabled US to
locate centers of seismic disturbance; but it
Is known that there Is a volcano or system
of volcanoes, whose action is frequently ae-
companied by earthquake shocks, in the
South Atlantic, about midway between
Guinea and Brazil, and another in the Bay
of Bengal, of Madras. Vessels sailing over
these spots have felt earthquakes or rather
waterquakes quite frequently. The bottom
of the Pacific is supposed TO be full of them.
Another belief, which originated after
the Calabrlan earthquake, is that the dis
turbance originates much nearer the surface
of the earth than has been supposed. Mr..
Mallet made thorough study Of that phe-
nOmenOn, and by series OF ingenious calcu-
latioDs was enabled to locate the seismic
focus from which the disturbance arose at
point five and three-quarter miles below
the surface of the earth. Perhaps the crust
of the earth in Southern Italy as on the
coast of South Carolina is unusually thin.
1t has been observed that few earthquakes
ever cross range of mountains, which is
explained on the theory that the mountains
must rest on a very solid and deep base
that offers resistance to the subterranean
force.
AT San Saliva dor there appears 10 have
been bat one shock, and that only of twenty
seconds duration. Destructive earthquakes
usually involve a series of shocks, sometimes
lasting for several hours, with brief inter-
missions. The earthquake which destroyed