Evening star., 1900-09-29
It Has Been Computed by the Coast
and Geodetic Survey.
WAS A WORK OF MANY YEARS
Methods That Were Followed in
Making the Measurements.
MATHEMATICAL ACCURACY
Written for The Evening Star.


The measurement of Mother Earth's ex-
act size and figure is monster feat of en-
cheering just completed by Uncle Sam.
1t has cost him nearly thirty years Of con-
stant effort and fully a half million dollars.
The scientific geographers of the world will
agree that the enterprise is well worth this
time and expense.
The honor of announcing to humanity Its
most accurate knowledge as to just how
large mass is our great spinning top, and
just what is its form and shape. falls sole
ly to the surveyors and computers OF our
coast and geodetic survey.
Mother Earth's diameter through her
great waistband, or equator. is discovered
to be 1896 miles; her height, from pole to
pole, 1889 miles. In other words, she is
broader than she is tall. Let us suppose
that there are two tunnels. dug in pre-
ciseiy straight lines. one joining the north
and south poles and the other connecting
two directly opposite points upon the equa-
tor-one, let us say, In Sumatra, the other
in Ecuador. Each of these great tunnels
Is traversed by an express train, running
at mile-a-minute speed. The trip from
the north to the south pole will require %
minutes less time than will that from Ec-
uador to Sumatra. In other words. the
earth is found to be that number of miles
fiattened at her poles.
AS to whether or not our sphere was In
reality fattened or elongated at the poles
had long been a mooted question. The con-
troversy was raging In the old world
century ago. 1t became so heated that the
geographers of that time found themselves
divided into two factions termed, each by
the other, the fiat heads or the 'long
heads" according to its opinion
The Question Settled.
Uncle Sans great survey proves that the
flat heads were correct But, after all,
this f1attening is slight that the human
eye, If proportionately large enough to
view the entire outline of the earth's figure.
as it may now observe an atlas globe would
be unable to detect the slightest irregu-
larity. Suppose We were to construct
miniature globe with dimensions exactly
proportionate to those of the newly meas
ured earth. Let this model have a diam
eter of six inches through its equator Ihe
diameter from pole to pole would be but
one-fiftieth Of an inch less. No one could
discern that this miniature earth was not
q perfect sphere unless he were to apply
a pair Of calipers.
The highest mountain ranges and the
deepest depths of the sea, If reproduced
upon this model earth, would be detected
merely as rough places, as indentations or
protrusions only 6-1 COO of an inch high or
deep. If this model earth were made oE
metal and were dipped in water the merest
wet film adhering TO It's surface would be
proportionate in depth to a great deluge
sufficient to cover all of our earth's dry
land.
BY this time the layman has begun to
wonder how Uncle Sans engineers could
have accomplished such a seemingly i'm
possible task the actual measurement Of
the earths dimensions In order to determine
the great spheres girth or circumference,
for instance, 1T would at first blush appear
necessary to circumnavigate 1t over the
equator and then across the poles, making
careful measurements step by step The
equator was not touched, however. during
the measurements, and needless is 1t to
state that the poles were not crossed. The
measurement Of a mountains height does
not require chat its summit be climbed Ii
we would yet be in ignorance as to
the insurmountable attitudes of our loftiest
peaks. Trigonometry, employed in noun
tam measurements, was utilized also in this
difficult computation of the earths dimen-
sons.
Longest Straight Line Ever Measured.
The longest straight line ever coyered by
measuring instrupaasss has playedS the all
important parNfin this monster calcStation.
eve might better call it the longest arc e,
the earth's curvature. Moline drawn upon.
a-curved surface can be. t3nicaIly speak
ing; ,srs!gh9... iG1is..s5aIeM the SNh
,..sss1 s..s..n jD - as that rat
after sweeping over the At
sZey1ee9!kes land very near to Cape May
FYfsffe house, on the southernmost tip OF New
Jersey. 1t then extends due westward
across Delaware bay, thirteen states and
the District of Columbia. At the California
coast 1t proceeds out into the Pacific from
near Point Arena, just north of San Fran
cisco. While this ares path across our con-
tinent has been traced upon our maps for
years and years. no one has hitherto known
its exact length from ocean to ocean And
would you believe it that 1T has taken Uncle
Sans surveyors since 1871 to measure it?
They had to determine it's exact length
also in degrees of longitude They of
course, knew that there is an agreement
between longitude and time; that the one
might be calculated from the other
They knew that the 800 degrees compris
ing a circle around the earth and parallel
10 the equator must equal the twenty-four
hours of time required by the earth i'm
making one revolution. Hence they set TO
work to measure the number of degrees of
longitude in the great arc by arranging
CLOCKS along its path and carefully com
pairing their time. The arc was found to
measure 4S12 degrees which must repre-
sent the sharpness of an angle made AZ
the axis Of the earth by two lines drawn
therefrom, one reaching the earth's surface
at Cape May and the other at Point Arena
Knowing this angle and the exact length
and curvature of the great arc, it was but
a problem In trigonometry to calculate the
distance between Cape May and Point Are
ma and the earth's axis. Simple formulas
gave the earths diameters. The fatten-
ing at the poles was calculated by aid of
smaller arcs measured before this the
greatest, was completed.
A Monster Task
One of these smaller arcs was measured
some quarter of a century ago from the
northern side Of Lake Superior down
through the southern portion of Illinois.
Another was measured hundred wears
ago through what is now Ecuador
The monster task. besides which all
others paled into insignificance, was the
measurement of the great arcs precise
length in miles from ocean to ocean. Not
until after twenty-seyen years of constant
field work was it proved that a chalk line
stretched from Cape May to Point Arena
and snapped against old earth's crust
would leave a white mark 2.6256 miles
long. And, by the way, 1t is along this
very line that our center of population
seems to have wended it's course westward
The distance was measured not along a
straight path such as would be covered by
a single tape, but along a narrow network
Of triangles. such the surveyor traces
in his measurements of great distances 1t
may be difficult of belief that the number
of localities whose latitudes and longitudes
were precisely established within this net