The Minneapolis journal. [volume] (Minneapolis, Minn.) 1888-1939, 1902-06-07
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ly. And that boom will swing whenever
the earth's crust moves.
The mast Of the instrument rests upon
solid column of masonry that seems as
stable and tmmovable as anything can be
In this world. Yet if the slightest lateral
pressure is exerted against the column
If one merely pushes it with ones hand
the boom will swing to one side.
If one Of these seismoscopes is placed in
q skyscraper it will show how much it
vibrates. II two were : placed in two
buildings on opposite sides of a street
they would show that the buildings tip
toward each other during the time Of
heavy traffic. Even hills will lean to-
ward each other when the Intervening
valley has heavy load OF moisture. -:
OF course there is an automatic ar
rangement which shows the exact second
Of the day when the record was received.
Inasnuch as it has been demonstrated
time and again just how long is the period
Of transmission through the earth, the
scientists can tell just when the earth
quake Or seismic disturbance occurred.
They can tell the difference by the pre-
liminary tremors and the character of the
recorded vibration. Each earth wave has
different signature that is as distinct as
the handwriting Of human beings:
More than once Professor Milne has
disputed cable dispatches as to the time,
place and severity Of an earthquake. and
he has always been right.
Many stations equipped with seismo-
scopes have already been established. Be-
fore long it will be possible to determine
the exact location of an earthquake,
whether under seas or on .and, with abso-
lutte precision. The distance from differ
emit points can be known from the seismo-
gram-that is what the record is called.
In other words, it may be known that an
&C RI n11o oil ia
lngton, so many miles from Argentina
and so many miles from San Francisco.
Mont Pelee's Record.
I When Mont Pelee exploded on May 8,
destroyed ST.. Pierre and covereda major
traction Of the island of Martinique with
! hot rocks and ashes and when La Sou
| triere followed suit on St. Vincent, the
delicate instrument in the cellar of the
| weather bureaus building received the
message. While it was written in a CT
| pher that is meaningless to the unframed
mind,-it is plain to the experts of the
bureau. The when and he where and the
duration Of the disturbance were re-
corded and also an idea of it's severity,
No matter how slight the tremor, pro-
vlded that 1t is distance away and not
a superficial disturbance, the inst rument
will record it. e
Each day the scientist who has access
to selsmoscope can survey the world
and know what is going on. It does not
matter whether mountains are shaken or
the earths crust at the bottom of the
sea is rent asunder.. The instrument re-
cords both with equal accuracy.
It is far easier to keep track Of earth
quakes than of volcanic eruptions. I'm
less the volcanoes outbreak is accompa-
MED by an earthquake-which it usually
| is, by the way-the seismoscope will have
no record of it. Then the scientific man
must depend upon the self-registering
barometer and that does not give very
exact information.
The barometers within a certain radius
all recorded the explosion of Mont Pelee,
but not until the reports are all in from
various meteorological stations will 1t
be possible to learn just how much is re-
vealed by them.
/ When the explosion of Krakatoa oc-
4 Cured in the Straits of Sunda, between
! Java and sumaltra, In 1883, the seismic
! air waves travelled seven times around
the earth, four times In one direction and
! three times in the other, taking about
thirty-six hours to make a complete cir
cult, rate of about 7oonniles an hour.