The Manitowoc pilot. [volume] (Manitowoc, Wis.) 1859-1932, 1906-05-17

quake at San Francisco and at Charles
ton, these have been of slight i'm
portance.
Authentic Data Needed.
Before the student of earthquakes
can say a certain district is likely &c
be free from seismic tremOrs a great
deal more authentic data must be &C.
CURED, As it is, all that can be said
OF any section of the country Is that
1t has or has not been frequently
shaken. The cause of the Charleston
earthquake for Instance, has not yet
been determined, but it is true that in
recent years the origin of many earth
quakes has been discovered. Many
others. however, cannot be accounted
for with certainty.
Seismology, like meteorology, is not
yet far enough advanced to announce
any invariable laws. 1t had been the
opinion that serious earthquakes never
occurred on low lands which had a
gentle gradient into the sea. The de
structlon of Charleston, while not null
llfying this principle at least showed
that it was not to be considercl as in
variable. On the other hand, there are
mountainous districts In which earth
quakes are of great rarity and in which
devastating shocks are unknown in
historic times.
Scientific study Recent.
N"bfIn oorfh1tInl-ac nay-a hnaD po+nI
for the last 5000 years. they have been
made the subject of scientific study for
only comparatively recent time. Many
circumstances are responsible for this
delay In attempting to collect and col
late data in a systematic manner. One
of the chief causes was the absence
of an instrument to record the move
ments and duration of the seismic ire
mors. The invention of the seismo-
Graph has Il lde possible the important
progress of late years. 1t records every
earthquake. no matter IN what part of
the world 1t Is central for every earth
Quake Is felt all over the surface of
the earth, but when it Is thousands of
miles distant the waves are not per-
ceptibe excepting to the delicatcly bal
anced instrument designed to respond
to the most feeble pulsaton.
Another valuable contribution to the
science has been the tables Of the dis
tlibution of seismicity prepared by De
Montessus de Ballore In these tables
the observations have been brought
down to the year 1897 in those districts
in which seismic occurrences have been
most frequent and best observed. They
include all earthquakes recorded in his
toric times, and list n total of 131 ,292
quakes and 10,499 epicentres, or points
of origin. The records, naturally, are
incomplete, but sufficient data are given
to show that earthquakes are of great
frequency, and that practically they
occur in every part of the world. The
tables also show markedly that GER
tain parts Of the world are especially
liable to be shaken, while In others
seismicity is rare or at least infrcquent.
Great Circle of Fire.
The so-callod great circle of fire"
around the Pacific Ocean is found to
produce the largest number of record
ed earthquakes. In Central California
alone there were observed between 1860
and 1897 no fewer than 1,096 earth
quakes ut 113 epiccnters. Dwarf, Japan.
is much more frequently shaken 1886
shocks being recorded at As epicentres,
or an average frequency of 24.14. The
mean average Of frequency at Toxic,
in the world. 1t should be remember