Evening star., 1923-11-28

tIOnllUueu from flTSl rage
administration building before a dis
tinguished audience.
Its most important parts are simply
seven and a half inches of tungsten
wire of exactly the same weight as
the filament of an electric bulb, and
three centimeters of No IL copper
wire, weighing just nine-tenths of
one gram. The tungsten wire. with a
thickness of eight ten-thousandths of
an inch. is made inert by fastening it
at either end to q brass plate by a
set-screw.
To this wire is attached the small
piece of copper wire. which furnishes
the solid mass" of the seismograph
and creates the trembling motion
when an earthquake occurs. In this
respect 1t duplicates the action of
the huge seismographs that hereto
fore have been universally used. To
prevent the wire from continuing to
vibrate. a small magnet is placed to
either side. and drop of castor oil
above and below the solid masS' ac-
counts for any tendency of the wire
to swing or initiate the motion of a
violin string.
eight millmeters, is attached to the
solid mass" and into it a beam Of
light is reflected through a prism.
This beam of light is thrown by the
mirror upon a piece of Photographic
paper wrapped around a revolving
cylinder. controlled by a carefully
regulated clock. The minute an earth
quake occurs it's tremors are trans
ferred to the wire, and the movement
of the light in the mirror is auto
matically photographed on the paper
giving a permanent record of the
tremor.
Present Instruments Large.
The pou t1Sad
weighs between 500 and 1000 pounds
1t is too bulky to record the hundreds
of tremors SO slight that they are
barely noticeable. but which indicate
the slipping movement that in time Is
believed to accumulate the pressures
that bring about severe rebound
which is an earthquake. In addition,
these monsters cost thousands of dol
lars, complete station representing
an outlay Of close to $4,000 at the
least
The seismograph brought out by
the Carnegie Institution costs less
than s25 and records not only long
earthquake waves but the smallest
ones. too 1t can be tuned" to rec
ord waves Of any length by merely
lengthening or shortening the tung-
was recorded by one tuned" for a
long wave and right beside it another,
tuned" for local shocks. was record
ing tremors beneath the surface of
California that never had been def
nitely known to exist.
This new seismograph was evolved
out of pure necessity as a result of
discoveries made by the Carnegie
seismology, of which DR.. Day is
chairman. So necessary was it to
obtain a record of the many little
shocks the larger machines were
u . &c
began experiments which resulted in
the instrument he demonstrated last
night.
To Test known Weaknesses.
These instruments, Dr. Day told his
audience, are to be arranged In
groups Of three. around positions of
known weakness in the earth S crust
in California, and also to find posi-
bic new points of weakness. One
will be to obtain records of waves
passing north and south, another for
those east and west, and the third
for those describing vertical mo-
ton. 1t will thus be possible to OBJ
tain so complete a record OF the
earth's movements.
In connection with his lecture, DR..
Day showed a map upon which were
charted the known movements or the
geologic currents in California. They
showed that in the last thirty years
the earth there has moved as much
southern California is pushing it's
way northward, 1t has been learned
the central California Is bound In
southeasterly direction, still other
portions are bound elsewhere, until
the whole looks as though it might
he describing a slow churning motion.
Another map showed the first sue
cessful effort to chart the definite
contour of the seas bottom and was
done by the photographic bureau OF
nnT ay~frr al
with the institutes committee in sels-
mology. 1t resulted in the dehnite
discovery of the so-called continenta!
shelf. a point beneath the sea that
takes a sheer drop OF from u,ooo 70
5000 feet off the coast OF California
Many Faults Mapped.
When it Is considered, therefore, DR..
jDay pointed out, that from the top
of the Sierras to the foot Of the con-
tinental shelf there is drop or some
Is 900 feet, in a little more than r.,
hundred miles. 1t is not quite so diff
cult to understand why that country
is one of frequent earthquakes.
1t has also been possible since tne
creation Of the advisory, commlttee,
the speaker said, to make what ne
believes to be the first map OF the
NAM faults that occur in the earth
crus- in California.
"O1t of this" DR.. Day continued
| "came the conclusion that all eartn,
o,Iakes in California had occurred
along along the well defined lines of def
mite faults. many of which, including
the San Andreas. or main fault, run
out into the sea. While l do not
| believe it will be possible to predlct
! inst when an earthquake will occur,
we shall know with positive certainty
| what is much more important to man,
kind-that is, where the next ones VIII
| shake the earth"