Evening star., 1898-12-17

ENIC/ words, We are soon
" to learn something
90 definite as to how
large mass the earth is and whether it
Is, IN truth. fattened at tha poles
This tremendous feat of surveying. inst
finished is the most extensive and vaIra-
bic contribution toward the solutions of
these problems thus far undertaken. and
which will leave them at rest for wears TO
come The survey has accurately meas
ured' IN feet and inches, the longest arc of
the earth's curvature ever covered bv
measuring Instruments. This line extends
from Cape May, y. j., due west over the
18th parallel TO the coast of northern Calf
fornia, forming more than q seventh of
that partic Ilar circle spanning the earth.
II mas required more than a quarter of a
century Of continuous work for the COM
PtetIon of the triangulation. The l,ngth of
the are having thus been actually meas
uFed IN feet and inches and fractions there
OF. and its curvature having been meas
uied IN degrees 10y aStronomiC work from
tAls length aud curry vaturc combined will
Iater be calculated, after months Of most
"LLIlcut computation, the actual shape and
tNpdHSe OF our sphere.
Rough Figures Heretofore.
true We have heard scme little con-
c FnInS the roughly estimated diameters
!
difficult to realize that nothing reasonably
accurate as to th6ss is Yet known. 1t has
beeh calculated that this colossal summing
top which We all love so well is NOT a rer-
1tct sphere. that it is thicker in diameter
through the equator than it is through the
PoleS- Theorists, even before Columbus
estimated that the earth was spherical wi
IL remained for Magellan's expedifinn fG
Prove this by circumnarigation Later
,i-gol-S'S nave SAID that it is not a perfect
sPhsre. ana II remains Tor the coast and
stu.tuc survey 10 prove or disprove this
10 ihe average reader il will at first blush
appear unreasonable that the Giameters of
thv earth through the poles and throu.h
lne equator can be calculated from such
Stid4Sht lines as this. Yet to mathema-
able.
The great are now completed intersects
PSFts OF New Jersey. Delaware, NIarvIana
NusH:'. west virginia. ohio, Indiana Hi
i-uiS' Missouri Kansas. Colorado Utah
Nevada and California, merely touching
" nor thefhmcSt corner Of the District Of
columbia The work was begun AT tho
tMo ends Of the line and the SURVEYORS
worked toward each other. \ few weeks
ago they closed the gap between th.u the
last stone being placed in the earth i'm Col
o'aeo. The arc was found to be > 60 stat
Ete miles in length. The actual area GOV.
tit4 by TN trdnscOntineEtal chain or ne,-
work OF trlangles for the marking off Of
which the surveyors have sucnt went
live years. does not cover the lines ns t6c
parallel at every point. IN some places
Wh"re "bstru' lions occurred, It was run
diIli@7lIe' which method gave accurate re-
suits, nevertheless.
Measured A>tronOmicaiIy
The great are has also been measured
aS'fohonicdliy, that is to say. in degrees Of
Longitude. There is. of course. an agree
meHt between longitude and time. the one
being readily estimated from the other
since the 90" degrees comprising, a cfrcIa
around the earth equal twenty-four boure
CT time Hence the number of degrees
winch the are measures should be r,adilv
learned 10y comparing clocks arranged
along the line. Consequently thirty-li,-a
tHtohUmsteTS were pat in place at yariCrIs
points and connected by telegraph. 4
ci'i7 'Meter Is very accurate clock used
principally to determine longitude at sea
1t Is adjusted so that changes in ternuera-
tufe cannot expand or contract its metallic.
WORKS and thus cause il TO run fast or
SLOW; Weeks are devoted to the regulation
vL throlpIrtteTs at the naval Observatory
EeFt- Inoy are corrected by the govern
InthJ astral clock. which takes its tine
from ihe stars. the sun not giving US cur
standard time directly. as commonly sun
posed Accuracy was carried to such a fine
POINT IN this longitude measurement that
even the time required for a telegraphic
fash 70 skip across the continent between
The stations was taken into consideration
The are was fUuud TO be 49, degrees long
y second set OF astronomical measure
intEts, not quite competed, will more def
hi-iy establish The points Of latitude be
sides these Of longitude. for the arc-in
ojher words. its exact distance in degrees
from the equator and from the poles.
These meaSurcTne eEts, considered in con
itC0on with The great arc newly siIryevtd
Will Wncn q simple formula is apnIiad
give the distance from either end TO the
center OF the Garth. The angle whicn would
ne formed at the center of the great
sphere by two lines one from the eastern
and the other from the western end Of the
arc. is Of ths same number Of degrees ms
The ar" Is long. Now. any one convcrsant
with iriSoncmstry can find the radius OF 81
hpheFe when the angle and the length of
the arc are thus given.
Many Smaller Arcs.
Further figures Will he obtained by using
measurements Of some smaller ares in CON
nectIon with this great one. There is an
arc well established, though small near
the equator, in Ecuador. Another has been
completed ON the Cape Of Good Hope In
Europe also there are many small arcs
which viii aid. Thus there are accurate