Evening star., 1923-09-16

mic disturbance, some interesting in
ferences have been drawn with re-
spect to the constitution of the in
terror of the earth. The complete
record shows two phases of pre-
liminary tremors" preceding the prin-
cipal waves. 1t is believed that while
the preliminary tremors pass through
the body of the earth, the principal
waves travel along or parallel to the
surface. Probably the first phase
represents the conversational and
the second phase distortional waves.
From the different rates of propa-
cation of the precursors it has been
inferred by r. D. Oldham that below
the outer crust, which is probably not
everywhere of the same thickness.
the earth is of practically uniform
character to a depth of about six
tenths of the radius, but the remain
ing four-tenths may represent a core
differing physically and perhaps
chemically from the outer part. This
same authority suggests, from his
study Of oceanic and continental wave
paths, that there is a difference in the
constitution of the earth beneath
oceans and beneath continents
The sounds that are associated with
seismic phenomena, often described
as subterranean rumbling and roar
ing,' are not without scientific in
terest. 'Isacoustic lines" are curves
drawn through places where the
sound is heard by the same percen-
tage of observers.
The advances that have beens made
in the study of earthquakes we're in
itiated in work commenced in Japan.
Years ago that nation, desirous of
gaining western knowledge, invited
a number of savants from other lands
to visit the land of the cherry bios
SONS. and these visitors were i'm
pressed by the frequent shakings of
the ground. Interest in these phe-
nomena gained more rapidly than
their frequency. and it was felt that
something should be done for their
systematic study.
At midnight on February %, 1850.
movements more violent than usual
occurred-chimneys were shattered or
rotated, tiles slid down roofs. and in
hama had the appearance of a city
that had suffered bombardment. Be
fore the ruins had been removed a
meeting was convened and the Seis-
mological Society of Japan estab-
lished. The twenty volumes of
original papers published by this
body summarize to a large extent the
results of the later study of seis-
mology. OF course, from time to
time meetings have been held and
other data has been added, so that
today there is a comprehensive rec
ord of earthquakes, their results and
causes.
RATHER F. A. TONDoRF of
II Georgetown University. who is
recognized as one of the leading au-
rhorities on the matter of earth
quakes, when discussing the recent
catastrophe said: There is no ques-
ton that this earthquake was caused
by the slipping along fracture The
older theory was that disturbances,
such as those that have just occurred,
were of volcanic action. DR.. Nauman
advanced the theory that earthquakes
were of tectonic origin. We find
many of the earthquakes to be along
lines of weakness in the earths crust.
This was not the way of those of
volcanic origin The latter were very
rarely of a severe nature. They never
were widely felt and consequently
were not recorded at any great dis
tances."
When asked as to whether or not
1t was possible to estimate where the
earthquakes start or. to phrase 1t
scientifically, where the slip occurs,
Father Tondorf said:
''These matters can only be arrived
at in a general way. for instance. in
a comparison of three stations. OF
course, however, 1t is possible some
times to indicate from a single sta
ton, noting the distance, but you
generally get only about or per
cent accuracy by this method. We
are aided in our work by the knowl-
edge that certain areas are sus-
ceptible; hence, we work by elimina-
ton"
Father Tondorf is not only a man
of the church, but he is scientist of
note, and combined with his extensive
knowledge is a charming modesty,
for, when asked. if his was not tho