Evening star., 1905-11-11
EARTHQUAKES.
Cause Of the Disturbance One Of Mys-
teries Of the Globe.

| From the Philadelph,a Ledger
The earthquakes which shook many towns
and cities in the Mississippi valley appear
| to have done no damage and to have served
no greater purpose, so far as the inhabit-
ants are concerned. than to give them
something to talk abOut In mid-August
| more engrossing for the moment than the
peace negotiations or even than the yellow
fever. 1t SO happens that the rarely deli
cate instruments with which the selsmolo-
gists-the scientific investigators of earth
quake phenomena--now record and measure
the movements withip the earths struc-
ture have revealed the fact that the hrm
foundations Of Mother Earth are not firm
at all: that tremors of some sort are or
daily and hourly occurrence. and that 1t is
only when the disturbance reaches some
degree of violence that 1t can be dignihed
with serious attention.
The tremors in the Mississippi valley
are chiefly interesting because they were
felt in a region far removed from those
portions of the earth's surface which by
reason of their confguration are generally
susceptible to such movements. AS the
vibrations in the earths structure are
transmitted through the earth instead OF
around it's circumference, and as they ira
verse great distances. the center of dis
turbance may have been many miles away,
deep In the rocky framework of our planet.
Accurate observations, such as those
made with the seismograph and other In
StrumentS, the tlme QlrectlOn ana
tGde of the vibrations enable the lnvestl-
gators to fix with considerable degree OF
accuracy the point of the disturbance. Tho
general run of earthquakes may be classed
as either volcanic in their origin or as due
to slips or fractures in the earth's crust,
the result of stress By far the greater
number belong to the latter class. those
due to volcanic upheavals being, as rule,
somewhat limited in their intensity and
area. On the other hand. the earthquakes
due to the breaking Of earth strata in
regions OF the earth where there is great
diversity in the surface, as in the vast
ocean deeps or in those places on the land
where the crust is turned up to form great
mountain ranges, are far more numerous
and destructive
The causes of earthquakes are bound up
to large extent with the unsolved mys-
teries OF this globe upon which we dwell.
and until We shall be able to explore deeper
into the interior than we have yet pene-
trated we must be content with the in
ductive reasoning Of the scientists. The
volcanic causes are obvious enough; just
as the railroads and iron mills set up SO
great a tremOf IN the earth as to disturb
the delicate observing and recording in
struments Of the astronomer and physicist
whose station happens to be near them,
so the vast steam explosions which occa-
sionally occur in volcanic phenomena create
greater tremors, which are dignified by the
name of earthquakes The larger cause
is found, however, in the readtustments in
the earths crust which are constantly go
ing on as result OF changing conditions
of pressure Such pressure changes may
be accounted for by contraction as the cool
ing process goes on, by the gradual denuda-
ton OF the continents, by the natural pro-
cesses of nature. or by the shifting Of the
atmospheric envelope. The stresses and
strains In the convoluted and twisted strata
Of rocks which make up the earth's crust
must be at times vast, beyond the power
Of the human mind to Imagine. When
the inevitable slips and breaks occur near
the surface, whether on the land or IN
the oceanic deeps, the effect cannot but
be stupendous The alterations in the sur
face are often attended by appalling con-
sequences to mankind-the outright deStruc-
ton of their habitations either by the mere
violence of the vibrations or by the en-
gulf1ng power of the waves set In motion
If the break happen to be beneath the sea.
Happily for us, the vast majority of the
but slight significance for the dwellers ON
tremors which shook Missouri and her
neighboring state must be assigned The
differences in the time at which the earth
quake was reported at different points may
be explained in part by the inaccuracy of
the observers, for while the vibrations
travel from place to place at varying speeds
from several hundred feet to several thou
sand feet per second-the exact differences
and their significance would require the
careful collation. and comparisons of all
the reports and their Verification Until
this can be had, not even a guess can be
made whether the focus of the disturbance
was near far whether the initial
shock was slight or severe.