Evening star., 1933-09-03

the mark is merely cut in the stone
monument, sometimes q circular brass
plate is countersunk and fastened per-
manently. Each one Of these Is what
Is called q benchmark and represents
work of the Coast and Geodetic Survey.
The brass plate has figures on 1t which,
to layman, are cabalistic. To sur
veyor they constitute sure guide. He
knows that he has before him an ab-
,olute landmark in the most literal sense
Of the word.
Surveys Measurements Final.
Sea level is the basis of Coast and
Geodetic Survey measurement. 1t is
the starting point for all Of its compli-
Gated system of guidance. By patient
calculations and actual observation 1t
has determined exact mean sea level
for every portion of the American coast
line The Chamber of Commerce or
Summer boarding house keeper of some
small town in Iowa, Michigan, or Colo
RADIO who wants to tell the world that
the place stands at a given altitude
above sea level must accept the meas
urements Of the Coast and Geodetic
Survey. And it makes no difference
whether 1t is in town on the Staked
Plains, hundreds Of miles away from
any sea and low lying or on top of a
mountain peak. the Coast and Geodetic
Survey will advise precisely what the
altitude Is to an inch.
So it Is obvious that in building res
ervoirs, In constructing highways and
bridges and any sort Of structure de-
signed to outlast the years, 1t is Of the
utmost importance to establish the
physical relationship Of that structure
to the environment in which 1t is
placed Gradients Of hills. the fall OF
cascades, the inclination Of slopes, all
must, in the final analysis, come to the
basic figures of the Coast and Geodetic
Survey to establish how they stand in
relation to the distant sea.
Geo is the godhead of the earth and
every science based on its structure and
mass relates thereto. Geodesy is the
science Of earth measurements and it is
this measurement which is the particu-
lar function OF the Survey But such
nice measurements cannot be related
solely to the earth. Astronomy must
have part. The Survey keeps in the
field. when its appropriations allow,
parties Of surveyors who constantly
check and recheck their measurements
and carry out the triangulation on
which the system is based The entire
country is covered by q network OF
these triangulations. In the Surveys
ofices at Washington, experts are in
cessantly going over the field notes and
making their immense calculations
which establish the shapes and levels.
the magnitude and the figure Of the
earth.
Sidereal dependence is necessary to
the Survey and an arrangement exists
whereby the United States Naval OBJ
Servatory transmits by radio frequent
exact time signals to Survey field par
ties. These are received, for example,
both Immediately before and immedi-
ately after the nightly star observations
made by the parties. Thus precise de-
examinations of longitude are feasible
Gravity and isostasy. geophysics. geo
desy and field astronomy, all enter into
the work Of the Coast and Geodetic
Survey. The merest peep behind the
scenes Of this bureau of the Govern
ment opens up vistas Of scientific lore
staggering to the layman and vet i'm
portant to him in his daily life because
all Of the work has practical applica-
ton.
1t is regarded as a fortunate thing
that the Public Works Administration
has decided that there should be no in
reference. through lack of funds. with
the work begun by Eratosthenes of Alex
andria. the Cyrene. some 275 years be-
1ore Christ and now carried on bv the
United States Coast and Geodetic Sur
vey.