Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-01-27
QUAKES PICTURED
BY NEW DETECT0R
GaIitzin Horizontal Seismo-
graph Is Placed in Service
at Georgetown.

A new Galitzin horizontal seismo-
graph, the only earthquake detector of
its kind on this side of the Atlantic
Ocean, has just been placed in service
in the extensively equipped Seismolog-
ical Observatory at Georgetown Uni
versity.
Said to be the most sensitive instru-
ment known in the field of seismic re-
search, Director Francis A. Tondorf,
S. j., had to construct for its protec-
ton a specially designed, double walled
cave" as the underground vaults of
the observatory are called. Unlike
other instruments, the Galitzin type
photographs" earth tremorS as they
are being recorded.
Utmost precautions were taken to
make the vault damp-proof and heat
proof. The seismograph's degree of
sensitivity is so great. Father Tondorf
explained, that if exposed to rays of
the sun, even indirectly through the
brick walls of building, the slight heat
would cause the instrument to tilt,
which means DETECTION of the needle
Strument together and concentrate the
needle required long and tedious
process.
Photography Held Important.
OF almost equal Importance to
Father Tondorf in recording the hori-
zontal movements of the earth is the
method by which this new seismograph
photographs" the tremors. When a
quake occurs 1000 miles or 5000 miles
distant the wave of tremorS are di-
rectly registered on a sheet which is
developed like an ordinary Photographic
plate. This proves not only great
time and labor saving device, but is also
valuable for preserving the records
The Georgetown observatory for sew
eral years has been equipped with o
Galitzin seiSmograph for the study of
the vertical movements of the earth.
With installation of the new machine
the observatory equipment becomes one
of the most complete in the world
The Galitzin machines are eompli-
Gated TO operate, Father Tondorf said,
and for this reason are not commonly
used. They have a very high intensivity,
and can register more distant Quakes
than others in use at the observatory
1t is highly important in seismic re-
search to have an accurate study of
the horizontal movements of the earth,
which are more destructive than the
vertical movements -..-.
The GalitZin machine, made in Eng
land, Is radically different from other
types In more constant use. Its weight
or pendulum, which Is so suspended as
to be in neutral equilibrium and to
which the point or needle is attached.
is Of only 25 kilograms, as compared
with 500 pounds for some machines.
Guard Against Heat Changes.
The "cave" constructed for the in
strument is about Is feet below the
surface. Double walls with electrical
heating keeps the temperature con-
stantly at about rs degrees Every
precaution has been taken to guard
the instrument from temperature
changes and external disturbance.
The seismograph, inclosed in her
metically sealed glass case, is mounted
on isolated concrete piers for steadi-
ness
Every morning and evening Father
Tondorf and his assistant, Father
Goberna of Spain, who is taking a
special course in. seismology, inspect
the SeismogramS, or records of the
various instruments. Since there are
about 5000 earthquakes year, or
about one every hour, records at George
town are very constant. Not all earth
tremors are recorded here, but, Father
Tondorf says, his two Galitzin instru-
ments will account for nearly all of
the intense quakeS during the year.
With the Photographic plates which
will now be made available to him,
Father Tondorf's work will be greatly
facilitated
1t is weird experience to stand be-
side one of these silent machines and
watch its pen" trace a zig-zag line on
revolving scroll of smoked paper
writing in Washington the story of a
quake that has just shaken up bit
of Alaska or perhaps South Sea
island.
THE earth does the trick" said
Father Tondorf. The seismograph is
simply writing machine with which
Mother Earth jotS down the record OF
her own restlesSness. However, it is
a peculiar kind of writing machine, fol
the pen is stationary and the paper
does the moving. If you can imagine
dexterouS photographer who can write
message by moving piece of paper
back and forth under fixed pen, you
have the system by which the earth
Easy to Locate Quake.
Reading these earth messages after
! they are recorded takes up much oil
Father Tondor'S time. Each zig-zae
mark must be accurately measured with
| the aid of microscope, but the mathe-
| NAUTICAL process by which the distance
of the quake is calculated is rather
| simple.
IF the seismogram is readable-and
often 1t is not" he explained, "a high
school child would be equal to the So
luton.
1.-THE secret is contained in this fact:
Earthquake vibrations travel in two
kinds of waves, one at the rate of 497
miles an hour, the other at 297l2 miles
an hour. Naturally the fast waves
reach the seismograph first and write
their signature. Later, the slow waves
| write theirs. Other kinds of waves also
| enter into the SeiSmogram, but the fast
| and slow waves are very pronounced
| and generally are easily identified. Since
| we know their speeds, and can tell from
| the space on the SeiSmogram the period
, elapsed between the arrival of the first
| fast wave and the arrival of the first
| slow wave, it Is an easy problem in
! mathematics to figure the distance that
| the two waves have travelled"
| To judge the violence of quake, the
seismologist relies on the zigzags traced
on the paper, allowance being made for
the distance travelled by the earth vi
brations. If the needle is joggled so
that it cuts wide zigzags. and the rec
ord shows the tremors travelled 5000 or
5000 miles. Father Tondorf knows the
quake was severe one. Slight quakes
5000 miles distant would make very
light record, perhaps none at all. Light
| quakes close at hand may make a very
heavy record.
| Father Tondorf mails to observatories
throughout the world a monthly record