Evening star., 1925-03-14

gravitational reflections of the
plumbline, due TO local masses.
For example, in Porto Rico, the
distance across the island is SO miles
but it was found that the old Spanish
astronomical observations made the
distance a mile greater than the
/ triangulation. Why? The center of
the island is a mountain and the
gravitational attraction of that
mountain mass threw the plumbline
out of perpendicular so that the
Zeniths of the two sides of the island
appeared a mile farther apart than
they were in fact.
In making his measures of the
earth, Hayford observed the exact
distances on land which, by astron-
omical observation, made a difference
of one degree, but the degrees were
not all the same distance. He then
corrected the astronomy by calCulat-
ing the influence of local mountains
in diverting the plumbline. That
necessity was unknown until he had
developed the science of isostasy-
the equilibrium of every section of
the earth, as compared with every
other section of equal area.
This theory of isostasy was first
suggested in 1850 by Pratt. but it
lay in desuetude until Dutton re-
ViVed 1t and gave il name, in a
lecture in 1889. Again it was ignored
until Hayford, then geodisist of the
United States Coast and Geodetic
Survey, developed it, between 1905
and 1909, and discussed its principles
in his book: The Figure of the Earth
and 1sostaSy, from Measurements in
the United States" Today isostasy
explains many mysteries and is ac-
cepted throughout all scientific cir
cles. BY it Hayford has made the
most precise measures of the earth
ever computed.
Now that the rotundity of the
earth, by the Hayford spheroid, has
been fixed, similar isostatic allow
ances will be made whenever the tri-
anglulations, upon known basic
points, differ from astronomical OBJ
servation. DR.. Hayford was present
ed in 1924 with the Victorian Medal
of the Royal Geographical Society of
Great Britain. Last week the news
that his measures had been accepted
by the International Society of Engi-
neers reached Chicago, just a day or
two after the scientist had died.
1t has been enormously stated that
all surveys in the United States ar
based upon the point now marked e.;
tilS NSl y SlOHSf pIdHltu pSl"tSH vic
White House and Ellipse. That stone
is the basic point only for the Lee
Highway surveys. All real estate and
highway surveys are based upon n
point located in what is known as
Meades Ranch in Kansas, located
there by the Coast and Geodetic Sur
vey, and marked by a concrete block
buried "a inches beneath the surface
and another block above 1T, protrud-
ing inches above the surface. That
point-12 miles north of the town OF
Incas-was established in 1891 as the
base for all surveys in the United
States, and later 1t was accepted by
both Canada and Mexico as their
base, so that now II is the one CEN
trail fixed point for all the continent
This Is the only continent in the
world which has but one point for
all surveys. The International Geo.
detic and Geophysical Union is seek
ing to establish similar bases in each
continent.
Congress has recently passed the
Temple bill, providing for mapping
the whole country, SO that all natural
features and improvements will be
recorded for every acre. The enter
prise will take many years and cost
$5o,O00,000, but would not have been
possible without the fixed starting
point on Meade's Ranch, together
with the Hayford measurement of
the earth and knowledge OF isostasy.
Copyright, 1925. by Paul V. ColIins.g