Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-09-13


is conducting experiments which are ex-
pected to revolutioniZe the study of earth
quakeS Already he has succeeded, for the
first time III history, in making synthetic,
artificial, quakes, Stimulating in a fashion
astonishingly close to nature all the terrific
strains and stresses Of the terrible cataclysm
that spreads so much terror and destruction
throughout the world.
The dreaded earthquake is one Of the last
oninous threats of nature. Men have pene-
trated most of the vast jungle mysteries They
have flown into the remote recesses OF the
Arctic They devising new means OF con-
uuerng strange and terrible diseases. Yet ever
since the white man first set foot on the Amer
lean continent he has been forced to confess
himself well-nigh helpless before the earth
quake. 1t may appear in any month, at almost
any hour of the day night carrying away
the very house he lives in as well as the loved
ones whose lives he strives to protect
Small wonder then, that the learned men OF
science are watching with the keenest interest
the important experiments of the youthful DR..
Leet His studies bring renewed hope OF Solv-
ing the many mysteries that have been bound
40 with the problem of earth shocks ever since
the dawn of history.
Hsurely no one is better qualified to explain
the revolutionary earthquake tests being con-
Quoted at Harvard than DR.. Leet himself
nationally known director OF the Har-
ward Seismograph Station. He points out: Our
experiments with scientific staff including
C. J. Roy and Allen Waldo have been described
as the manufacturing OF artificial earthquakes
Made by a small charge of dynamite, the shocks
used in these tests move the ground so little
that instruments which magnify disturbance
10000 times have to be used to get a record Of
them
lust what Is an earthquake? A striking
- Illustration is offered by DR.. Reginald DAILY,
also distir guished scientist at Harvard
when with your hands you bend stick
until it breaks the sudden snap sends vibra-
tionS often painful, along muscle, bone and
nerve Of the arm. The strain of the stick IS
relieved by fracture and the elastic energy
accumulated in the stick during the bending is
largely converted into the energy of wave
motion.
an a somewhat similar way the rocks OF
the earth's crust have been and are now being
strained Every day, somewhere in the world,
they swapping and sending out elastic waves
from centerS, The passage OF
these waves in the earth we call an earthquake,
or seismic disturbance.
"a majo quake has enormous energy. At
and near the center of shock it skaters the
works of man and may rupture into the very
hills and mountainSideS. AS each wave spreads
into the earth, the intensity of the vibration
falls very rapidly, that not many hundreds
of miles from the center the heaviest shock
cannot be felt by human being. Much less
can he, at the other side of the globe feel
the impact of a wave which has plunged to
depth of thousand miles or more and energies
under his feet.
ain order to watch and time accurately each
I'VE as it makes its long journeys around and
through the earth, highly sensitive instruments
are used Those wonderful devices, called seis-