The National tribune., 1906-04-26


earthquakes have always deeply en-
gagged the attention OF thinking men,
and the most determined efforts have
been made to discover their causes and
laws. Up until 1879 only superstitious
views prevailed. Then q scientist as
serted that they were shocks of natural
forces. operating according TO regular
but wholly unknown laws. The wave
theory began to be advocated in 1850,
when it was attempted to explain the
formation Of the Alleghanies in this
way. The really accurate study of
earthquakes may be said to have be-
gun by the writings Of Mallet in O re-
port to the British Association of
Science in 1S47. In 1857 Mr.. Mallet
pcnse of the Royal Society of Great
Britain, and began the establishment of
the science Of seismology upon the basis
Of accurate observation. His conclu-
sions are generally accepted by scien-
lists to-day, with the exception that
they believe that an earth-tremor is not
due to any one cause, but to several
Mallets theory is that the earth was
once a hot fluid globe, which on cooling
had first u thin crust. This in turn
cooled more rapidly than the interior.
and was consequently torn into assures
at various places by its own contrac
ton. This exterior crust became coy
that its conductivity was greatly les
sened and it did not respond so readily
to the passing off of the interior heat
AS the cooling, however. progressed be-
low the crust 1t was subjected to great
strains by reason of the changes in the
interior of the earth, and all the time
were brought about differences of pres
sure, owing to the elevation Of great
mountains, the weight Of oceans. etc.
From these unequal distributions Of
weight around the earth's surface como
much Of the force which develops into
earthquakes. These immense pressurcs
may at any time or place be transmit
ted into heat and produce volcanoes,
and other violent phenOm-
cna. According to the experiments
MalIet made on crushed rocks and other
calculations, he arrived at the conciu
sion that tho known volcanoes dissi-
pated less than one-tenth of the earth
He regarded earthquakes and voica-
noes as preventative rather than de-
since they were adjusting the
crust of the earth to the constantly
shrinking interior.
Attempts have been made to connect
earthquakes with the suns and moons
therefore, with high tides
and low tides, with atmospheric condi-
lions and with Winter and Summer.
These have been successful only in the
list Of known earthquakes showing a,
greater preponderanee for the Winter
months than for the Summer. Prof.
Milne reckons that there Is at least one
daily in Japan and probably
from IS TO 80 on the earth's surface.
The most earthquake-shaken region
Of the world is 1.-The ring OF fire" which
encircles the entire Pacific Ocean.
There are volcanoes all around the Pa
cific, and the shores Of the ocean slope
much more sharply to the sea than
those of other. countries where no
are known.
Earthquakes are felt either as YER
teal shocks coming straight up from
below: as horizontal or lateral shocks
and as undulatory or wave movements.
1t is not impossible that all these are
the result Of the same disturbance.
That is, disturbance may occur att
some point five or six miles, or even
more, below the earth's surface, and
a portion of it's force di-
rectly upward. while the rest, radiating
self at some places as horizonal and att
others in a wave-like movement. Mr..
Maliet believed that the centrum of the
earthquake of 1857 was five
and a half miles below the surface, and
that no earthquake impulse has everI
deeper than 80 miles.
Prof. Mines studies Of the Japan
led him to believe that the
great Yokohama earthquake of 1891
started somewhere between one and al
half and five miles down.
These disturbances extend over vari-
Gus magnitudes. 1t is believed that the
great earthquake Of Lisbon in 1861
shook an area four times as great as
Europe, and may have shaken the whole
globe.
Mr.. Mallet divided earthquakes intoi
three classes. The first Great EARTH |
quakes" have diameter Of about 1000
to 1900 miles and destroy cities, kill
OF people and dislocate great
portions of the earth's surface. His
second class he called "Mean earth
luakes'' which have a wide superficial |
area. but do less damage. These may
have diameter of 400 miles. His third
class, minor earthquakes" in which |
buildings are shaken and sometimes
have diameter of between
100 and $50 miles.
Among the memorable earthquakes
may be noted that of Lisbon, Nov. /. |
1856, which left the city a heap of
ruins, destroyed $4,000 lives. and was
felt from the Madeiras to Britain; that
which destroyed Aleppo in 1922; that
1T Mount Ararat in 1910; at BrOussa,