Evening star., 1942-08-25
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Laboratory. Field
And Study
BIZ Thomas r Henru

ANU StuOy
By Thomas r. Henry.
An incredibly sensitive instrument is
being used by prospectors OF the United
States Bureau of Mines to locate hidden
sources of minerals essential to war
This is the gravity meter which
records the gravitational attraction OF
dot on an 81"
1t can record the presence OF units as
1nf1nitesimal as q 300-millionth part
of an ounce.
This instrument now Is In use In a
survey Of two Arkansas counties for
bauxite, the basic mineral from which
aluminium is obtained. Investigations
IN the past have shown that bauxite
usually is associated with a type of
granite known as syenite which usually
is more dense than surrounding or un-
DERIVING rock. Everything in the uni
verse attracts everything else by the
force OF gravity. An increase in the
attraction in q certain direction over a
given locality indicates the presence of
heavier rock.
The gravity meter is probably the
most sensitive instrument ever used In
extended field operations. It's tempera-
ture must be kept constant at all times
within a few thousandths Of degree
by means of an electrical heating coil
controlled by q delicate thermostat.
Windows Of the auto in which it is car
ried are blinded to keep out the sunlight,
and the instrument is suspended by
spring cradle in the car.
When operating along a highway the
gravity meter is never removed from the
automobile. A hole in the floor permits
the observer to drop q specially built
tripod to the earth, mount the instru-
ment on 1t, and take reading for that
particular point. II 1t Is necessary to
transport the device across fields 1t is
carried In a special device on mans
back, or swung between poles like
stretcher.
Users tell the following experience to
indicate the meters sensitivity. A piece
OF blank paper was placed on the meas
uring system and the instrument was
balanced to center. A f1ve-letter word
was written on the paper. There was
an observable detection of the needle.
An additional dot over an Il" caused q
further detection.
The gravity meter is used in connec-
tion with another device almost as sensi-
tive-a magnetometer. The synetite is
more magnetic than most rock. The
instrument is easily disturbed by the
presence Of small bits OF iron or Steel
The operator cannot carry pocket
knife or even = steel belt buckle.
When the magnetometer and the
gravity meter coincide In their deflec-
tions there is likelihood that there are
bauxite deposits In the neighborhood.
Actually thousands Of such observations
must be made over relatively small
territory before results are obtained on
which much reliance can be placed.
On the summit OF Mount Wilson, site
of the worlds largest astronomical OBJ
seryatory, a remarkable phenomenon is
shown occasional visitors-the ability Of
man to move mountain merely by
commanding it to move.
Just say in firm voice: Move over,
Mount Wilson" The mass of rock
weighing billions OF tons moves without
protest.
The reason one knows 1t moves Is
that needle on one of the most delicate
seismographs ever set up records an
intinitesimally minute earthquake
caused by the soundwaves set up by the
voice striking the side Of the mountain.
A stamp of the foot brings vigorous
response. Deer running over the noun
tain slopes badly mess up the record.
At the foot OF the mountain. in a
laboratory Of the California Institute OF
experts on earthquakes Is making use
of just such minute earth shocks for
some essential war purposes. They are
caused by variations of pressure in the
atmosphere passing over various parts
Of the earth's surface. At present, DR..
Gutenberg explains, 1t Is possible to tell
the approximate weather in certain
distant part OF the earth by the record
Of these Shocks"
They also vary with the tides striking
the shore and it Is possible to detect
cannonading at sea and, in some cases,
the kind of shells in use.
Much Of the work is carried out In
close cooperation with the War and
Navy Departments and all details are
military secrets
The fact remains that the extremely
minute "earthquakes"-or moving of
shock waves through the earth-con-
stitute sort of automatic telegraph
and that very little of violent nature
can happened within hundreds of miles
without transmitting the broad outlines
Of Its own story.
Criticizes Checking
OF Seekers Of Recreation.
To the Editor Of The star
read with amazement that Leon Hen
derson's office, or gas-rationing Office
| in MARYLAND oneratirp under his illriS.