Alma record. (Alma, Mich.) 1878-1928, 1886-10-22

limit must have been considerably cx-
ccedcd at Charleston. In New York
chandeliers and doors were made 10
swing throug considerable arcs, but tho
extent of SWING depends more on the
violence than the amplitude Of the in
itial impulse.
After the Neapolitan earthquake of
1857 Mr.. Malet, by careful examina-
ton of the cracks produced in buildings
and the direction in which bodies were
throwa, estimated tho focus TO be n fs-
sure nine miles long, the point OF great
est commotion being near one end OF 1T
and not more than ten niles below the
surface. BY the use of seismometers
the direction of motion and angle of
emcrgence may be registered at many
different places around the same focus.
BY comparing these and noting the
time at which tho shock occurred at
each seismometer. the position Of the
focus and the rate of transit through
the ground may be computed. Tho
depth is rarely more than twenty miles.
Japan is continually shaken by earth
quakes. and from observations on seiS-
mometcrs in that country the follow
inc results have been deduced:
l. Different earthquakes across the
same country may travel with different
velocities varying from few hundreds
of feet TO two miles or more per second.
2. The same earthquake travels
moro rapidly near its focus than across
regions remote from it.
8. The greater the intensity of the
shock the greater is the velocity of
transmission.
Earthquakes have been artifcially
produced by the explosion of gunpow-
der or dynamite under ground. The
rate Of transit for shocks produced by
gunpowder was found by Mr.. Mallct TO
be S25 feet per second in sand and
1905 feet in granite. Dynamite eX-
plosions are more sudden and violent
than those of gunpowdcr. An explo-
sion of 80 900 pounds OF dynamite was
effected at Hallett's point in 1876.
Through the neighboring country the
rate of transit of the shock varies from
5000 TO g. 00J feet per second. About
100000 pounds of dynamite were ex-
ploded at Flood rock in October of last
year The rate through the same coun-
Try varied from 5000 to 20, 900 feet per
second, or, say. from one mile to four
miles per second being fastest where
the ground is hard rock and slowcst
where it is sandy.
1t is scarcely possible at the present
moment TO estimate the velocity Of
propagation of the earthquake wave of
Tuesday night from the accounts thus
far telegraphcd 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 compar son 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 reg ons OF alluyial deposit
Charleston and Savannah are built on
beds of low, fat. sandy country, hun
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 1866 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
foundation of basaltic rock and hard
limestone. escaped entirely.
In soft ground n violent earthquake
nearly always produces cracks. which
often close just after the passage of
the wave. In many eases they arc left
as open chasms of great size. In an
earthquake thar occurred in the West
Indies in 1892 human beings were
swallowed up by assures that closed
over them. Some were caught as if in
trap and gripped thus until death
ended their suiferings.
Many OF the greatest earthquakes
hitherto recorded have started from
foci under the sea near the coast. In
such instances n 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 n 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-wavc that