The National tribune., 1906-04-26
NATURE OF EARTHaUAkEs.

and the most determined efforts have
laws. Up until 1879 only superstitious
views prevailed. Then q scientist as
| serted that they were shocks of natural
| fcrces. operating according TO regular
but wholly unknown laws. The wave
| theory began TO he 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 a re-
port 10 the British Association of
/ Science in 1S47. In 1857 Mr.. Mallet
| published his complete work at the ex-
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 carth-tremor is not
due to any one cause, but to several.
| MallctS theory is that the earth was
once q hot fluid globe. which on cooling
/ l4ettl ift AZ tiiIi VI ust- iiio IA h'i "a
cooled more rapidly than the interior,
and was consequently torn into assures
at various places by its own contrac-
| ton. This exterior crust became cov-
cred with sand. earth and vegetation, so
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 II 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 come
! much of the force which develops into
earthquakes. These immense pressurcs
may at any time or place be transmit
I ted into heat and produce volcanoes,
earthquakes and other violent phenom-
| cna. According to the experiments
Mallet made on crushed rocks and other
! calculations, he arrived at the conciu-
sion that the known volcanoes dissi-
| pated less than one-tenth of the earth
heat, which is known to be passing off.
! He regarded earthquakes and yolca-
! noes as preservative rather than de-
structive, 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 moon: I:
extraction; therefore, with high tides
and low tides, with atmospheric condi-
tions 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
earthquake daily In Japan and probably
from 25 TO 80 on the earth's surface.
The most earthquake-shaken region
| of the world is 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
earthquakes are known.
Earthquakes are felt either as YER
ticai 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 at
some point five or six miles, or even
| more below the earth's surface, and
| communicate q portion Of its force di-
rectly upward, while the rest, radiating
out from this center. will manifest it.
| self at some places as horiZonai and at
| others in wave-like movement. Mr..
| Mallet believed that the centrum of the
| Neapolitan earthquake of 1857 was five
and a half miles below the surface, and
that no earthquake impulse has ever
started deeper than 80 miles.
Prof Mines studies of the Japan
earthquakes led him to believe that the
! great Yokohama earthquake of 1880
started somewhere between one and a
half and five miles down.
These disturbances extend over vari-
Gus magnitudes. 1t is believed that the
| great earthquake Of Lisbon in 1856
| shook an area four times as great as
Europe, and may have shaken the whole
| globe.
| Mr. Mallet divided earthquakes into
three classes. The first Great earth
quakes' have a diameter of about 1000
to 1900 miles and destroy cities, kill
rlultitudes of people and dislocate great
portions of the earth's surface. His
second class he called MEAN earth
quakes'' which have a wide superficial
area, but do less damage. These may
| have q diameter of 400 miles. His third
class, Minor earthquakes" in which
buildings are shaken and sometimes
nssured, have a diameter of between
100 and $50 miles.
| Among the memorable earthquakes
| may be noted that of Lisbon, Nov. /.
1855, 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
at Mount Ararat in 1910; at Broussa,
Asia Minor, in 1855; at Quito, 1859:
| Mendoza, South America, 1860; Ma
Mia, 1863: in Peru. 1868; Cuenta, in
Columbia, 1875; Manila, 1880; VAL
| paraiso, 1880; Ischia, 1881 and 1888;
the earthquake phenomena accompany