The sun. [volume] (Morris, Stevens County, Minn.) 1882-1895, 1886-10-07


second, or. Guy, from one mile to four
miles per second. being fastest where
the ground Is hard rock and slowest
whore 1t 10 sandy.
It il scarcely possible at the present
moment to estimate the velocity OF
propagation of the earthquake wave of
Tuesday night from the accounts thus
far telegraphed and published in the
morning papers. Nor are we yet
furnished with sufficient data to esti-
mate the position of the focus. Con-
lectures have been already expressed.
but careful comparison of many observa-
tons is indispensable.
The effect Of an earthquake shock is
usully far more disastrous on beds
of sand or clay than on solid
rock The recent shock has been most
violent in regions of alluvial deposit.
Charleston and Savannah are built on
beds of low, fiat, sandy country, hum
dreds of miles away from the rocky
regions of the Alleghenies. Most If
not all of the cities that have been
destroyed by earthquakes have been
situated on soft ground.
In 1865 the most disastrous earth
quake on record passed under Lisbon.
The lower part of the city, built on
clay. was utterly destroyed. All of the
buildings in the upper part. resting on
a foundation of basaltic rock and hard
limestone. escaped entirely.
In soft ground violent earthquake
nearly always produces cracks, which
often close just after the passage of
the wave. In many cases they are left
as open chasms of great size. In an
earthquake that occurred in the West
Indies in 1892 human beings were
swallowed up by assures that closed
over them. Some were caught as if in
a trap and gripped thus until death
ended their sufferings.
Many of the greatest earthquakes
hitherto recorded have started from
foci under the sea near the coast. In
! such instances great wave is produced
over the point of disturbance and
spreads out, followed, of course, by
others from the same point. If due to
the faulting of the sea bottom we may
easily understand how the sudden up
lift of one wall through hundreds of
feet would be cause capable of pro-
ducing a wave many times higher than
any that have swept the shore under
the action of the wind. The destructive
effect often exceeds that of the earth
wave. Many instances have been re-
corded of ships being lifted up and
stranded far inland. The sea-wave that
followed the earthquake of Lisbon
reached the shore an hour after the
lower part of the city had been destroy
ed. By the falling of houses $4,000
people had been killed. An equal num-
Der persisted before the series of great
waves had exhausted their energy,
making 10000 victims in single city.
The height of such waves has been
estimated, on good data, as much more
than one hundred feet.
From the fact that no sea wave has
swept up the Savannah river, and the
rumors of flooding at Charleston have
not been confirmed, it may be conclud-
ed that the focus OF the recent EARTH
quake is not under the sea in the neigh
borhood of the worst-shaken cities.
Sea waves produced by earthquakes
near the South American coast have
made the entire passage of the Pacific
ocean with energy enough to make the
circuit of the globe except for the in
tervening continents.
By comparison of records covering
long periods of time earthquakes have
been found to be very slightly more fire.
quent in winter than in summer, and at
times when the relative position of the
sun and moon is such as to produce the
highest tides. But no intimate relation
between earthquakes and the miner
fluctuations of the weather has been
established on any basis of careful OBJ
servation. At certain points the earth S
crust may be in a condition of strain.
almost at the criticize point of rupture.
A prolonged depression of temper allure
tends to increase the contraction, and
an earthquake my possibly be thus de-
termined. The moons attraction may
likewise increase the strain very slight
ly. But beyond this the weather
prophet of earthquakes is left to moth
ing better than conjecture.
In volcanic regions the escape Of
soluble gases through minute cracks in
the ground may serve as an indication
of subterranean disturbance by alter
ing the taste of m neral springs. This
has sometimes excited lucky conject'
ures of approaching earthquakes as the
forerunner of volcanic eruption.
Rambling in the ground is not infre
quently very brief forerunner. But
such signs are very unreliable, and nc
method of predicting an earthquake has
vet been discovered. Immediately aft
er a shock there are always claimants
for the honor of having guessed its ap
proach, but invariably they are unable
to give any definite ground upon which
, the relation between cause and effec
can be traced. Stories about peculiar
conditions Of the all, or of the human
! system. or about the terror displayed
by animals, as premonitors Of earth
quakes are exclusively the products o
superstition.