Evening star., 1921-01-02

was conceived to be a subterranean
hog; in India, a mole. The Mussulman
! pictured it as an elephant, while in
. North America the tortoise rocked the
crust. In spite of these wild attempts
I to explain th-shakings it is noted
| that classic writers touched on the
scientific reasons. So Pythagoras and
Seneca ascribe auakes to the presence
of masses Of fire at the earth's cen
ter, Aristotle to pent-up gases. Lu-
eretiuS fancies them the consequence
of the undertakings of rock strata
due to water agents, while Democritus
recognizes them as the consequences of
upheavals and subsidences of the
mathematician and philosopher, pOpu-
| lar about the middle of the sixteenth
| century,. figures that all seismic
energy is the resultant expression of
| the chemical action sbstweeAs the salt-
petrous. bituminous Ahd sniphurous
| accumulations in the earth.
"Kauman, writing in 1850. classified
earthquakes as volcanic and tectonic,
| the former being due to volcanic ex-
posions, the latter to movements in
| the rock masses. The Importance of
this latter class has grown with time.
and 1T is now most generally accepted
that all the really heavy quakes are
| to be included under this type, and
| that those of volcanic origin are of
slight Importance. This belief is
strongly borne out by Father Miguel
Saderra Maso, director of the Philip
pine chronological observatories, who
declares: Beyond a doubt. many seis-
mic disturbances are due to causes
other than yulcaniSm. Many of the
worst disasters We have experienced
have nothing to do with volcanoes.
and that volcanoes are nearby is only
coincidence, or may be explained by
the fact that the place where great
| disturbances in the earth's crust occur
| is naturally zane of weakness and
/ where molten material would be ex-
pected to seek AN outlet. At the time
OF the Messina earthquake Mount
Etna, which can be seen from Messina,
was comparatively quiet. The great
disturbance at Messina. as is general
ly known. was due to an adjustment
fracture in the eapth's crust which is
marked by the Straits of Messina'
! The great California earthquake of
April, 1906. is another striking in
stance of disturbance due to dislo-
| cation. The shifting was along the
San Andreas fault the slip measur-
ing a distance of 270 miles. in which
the two sides of the fracture had been
displaced relatively to each other by
an amount varying from a maximum
of twenty-one feet to an uncertain
minimum, but which must have dis
! appeared entirely at the ends of the
! fault. AS a striking example of an
earthquake. due primarily to vulcan
ism, / might cite the cataclysm OF
Taal, p. /. Yet 1t should be added that
the volcano is located along a line OF
crustal weakness, and at the time OF
the quake very appreciable dis
placement occurred along one or more
lines passing through the Taal vol
cano.
"The practical certainty of the dis
location theory calls for a more thor
ough study of geological formations
so that the more unstable areas may
be indicated on the map. This accom-
plished, a more exact Interpretation
of the warnings given by lesser
shocks. would be useful in places sit
uated along a serious fault line. Had
this been done in the past. Messina
and San Francisco would have been
better prepared to meet the shocks
that were so disastrous for them.
y
or EPEATED attempts have beer
~ made to establish some connec-
tion between magnetic and seismic
disturbances with view to predict
ing the latter. Yamasaki reports that
for three days prior to the grea,
Japanese quake of August 81, 1895, in
North Honshu, the magnetographs al
Sendai, Toxic and Nagoya were vio.
lently agitated. Nakamura chron-
icled like magnetic phenomena pre-
: ceding the great Japanese seaquakt
of the same year. Prof. Milne, the
noted English seismologist, says these
magnetic disturbances may of course
be regarded as mere condolences. bu
that when We consider volcanic anG
seismic activities as evidences o.
physical and chemical changes. to.
gether with mechanical displace.
ments of a molten mass, it Is reason.
able to suppose that they should hav'
at least local influence upon mag
s netic needles. Quite few seismic
Y observatories. favorably located. hav,
within recent years. added magnetic
! ! graphs to their equipment with
4 view to settling this question. II
2 case a correlation is established Ii l,
) just possible that a rule for earth
. ! quake forecasting will be at hand"
81 One of the earliest known reports
$ of an earthquake in North Americ;
S was chronicled in 1868 by the Jesui
lmisSi0nary- Pere Charles Simon. Thil