The times. [volume] (Richmond, Va.) 1890-1903, 1902-02-09

THE MEASUREMENT OF TIME.
ibis Wholly Dependent Upon Science OF
Astronomy, aud Without 1t the Nav
ipa,lon OF the Seas Mould Be
an Imposs.biIity.
written for The Times by Prof. w. A
Gathrlgnt.)
There are some VINO are inclined TO INT
Jelief that from unitarian point OF We"
ne science OF astronomy is TO pc SUP
5Jrdinated to the science of physics AM In
nemistry. They commit a mistake, TO-
lot even such practical sciences as tht
asst two named have mad such dlrec'
fearing upon practical ana everyday III.
IS astronomy. Without a knowledge o.
hat great science we should have no ac.
iurate means of measuring time, natlea
ors would hopelessly lose themselves u
ne painless waves Of the sea. accurate
eodetic and topographic neaSurenen nj
would present insupe aUle difficult es, suCh
.actlcs1 amt indispensable things as cai
ldars and almanacs would not exist; /
hort, there would prevail inextrlca Die
onfusion in regard to many thtngs.
Even such as have but little conception
If scientific matters will readily under
and that the ton Of places by Ions
tude and latitude is OF the creates. I'm
,ortance. The mariner that wants 70
sail for a certain island or certain naI
ON until he inadv rtently alights upo ] III
place Of destination. He knows the long
tude and latitude Of the latter ana M mt
.ails towards it as directly as otne1 CIT
stances would hermit. 4
ii''' @s'li~ NAUTICAL SCIENCE.
Now, here present themselves two DIS
First. : The Obtaining OF the longitude
nd latitude of places on the surface o.
he earth, and. after these are estaollsh.
ID, how the navigator gets there wltnous
al Science is nothing but branch Of as
:ronomy and without at least pracuca
knowledge Of it the mariners would DC
40 more than os fhe
economical science enable the nautical
man to find out at any time on the ocean
exactly where he is and to arrive whert
re wants to co. IN mere ne"spape' o.
icle we cannot be supposed to enter min
ltely into an explanation of the more ant,
ess ingenious methods of finding the long
tude and latitude of places on the sur
face of the earth and we conflne Our
lives to an example in each case Let
is take circumpolar star. that Is, on
hat does not set. This star will. within
wentyfour hours. twice pass the n1er.
1ian, or, to use technical expression.
Eliminate Let this star be observed a.
it's upper and lower cuImination with
suitable instrument enabling us to reao
off the altitude Of the star at its two
EXAMINATIONS. The mean Of these att
tudes will give US the latitude of the
place There are other methods which tim
and space forbid us to mention; This
for the determination of latitude. The
'ongtitude Of a place is the di ference of tn
fi,,o of no other
Greenwich for instance. Now. the deter.
mination Of local time is accomplished
by observing celestial object and per
s'I CEIE EST IA. oBJECTs AND HOW
MEASURED.
A person not converSant with the won.
and its applicability to celestial bodies
that are hundred thousands. nay billions
of miles distant from the earth. cannot
but wonder with feeling OF ave Re- nov 10Y
.ance of the sun and planets can be meas
red. and still this problem IS not so diff
icult Of solution as many others The
,ngIe under which the radius of the ear
would appears when viewed from the
noon or the sun or planet is called the
,arallax Of the celestial BODY. and wher,
the latter is on the horizon it is called
horizontal parallax. The radius of the
earth being known and also 81, the para alsas
the earth is easily calculated Thus have
been found the distance or the moon and
sun from the earth. The third OF the
tablishes the relations which exist he
tween the sidereaI periods Of two planets
and their respective distances from t1s
sun, ena bles us to find the distance IT an
planet. its sidereaI period that Of the
earth and the distance of the latter being
known. The synodical period Of a planet
which is the time occupied by 1t in m sc
ing from conjunction to conf notion. be
observed. the sidereal period can be east,
ly computed.
This method of finding the distance o.
The planets requires. therefore. an accu-
rate determination of the earth's dis
lance from the sun. and for this reason
the most strenuous exertions have beer
made to obtain as accurate value Of t'''s
1istance as possible AS we have mention
ed before. the distance can easily, y
found after establishing the s1n's roz
zontal parallax, and for this reason it Is
| this parallax. At the beginning of the
| last century no result had yet been at
tanned that might be called approximate,
correct and it was not until a compare
lively recent time that trustworth,
value of this horizontal parallax Of th'
| sun was obtained. With this more &C
curate distance of the sun from the eartl
has been established. The method EN-
oIoyed in a satisfactory solution Of this
| important problem displays an amount o
ingenuity that cannot fail eXcite tbs
admiration Of those who are capable o.
appreciating such mental labors.
DISTANCE OF SOLAR SYSTEM.
| AS to the distance of the bodies tina
| Constitute our solar system, science ha:
nlaced matters on pretty sure basis
| but the ever active and inspiring human
mind was not satisfied with this and /
nas striven and IS still striving to gauge
| the very depth of the steller universe.
| loes not require any special acuteness o
| the intellect to see thut such a paralla1
rs that of the sun anc the moon or thu
| planets is not possible in case of tn
stars. In comparison to their stupeudou
distances from US. the radius of the eartf
'windles into ma thematical point thai
s. into nothing, and it became indspen
| able to find a parallax that related Il
| ,meth'rg incomparablv larger thar
shat radius. It suggested itself to as
| eronomers to choose the radius Of tn,
| ,arths orbit for the line to base thu
| .aralax Of the stars on and this paral
| iax has been appropriately called the an
lual parallax. The number Of star!
whose annual parsllax has been obtained
With more or less reliable exactness i!