Evening star. [volume] (Washington, D.C.) 1854-1972, 1890-01-20
HOW THE EARTH MOVES,
Prof. Searle Talks at the Catholic Uni
versity on Its Spherity and Motion.


The second lecture Of the public astronomi-
cal course by Prof George NJ. Searle at the
Catholic university on Friday afternoons was
delivered last week on the subject Of. the
spherity and motion of the earth. The lee
turer asked his hearers to imagine themselves
on the deck Of an ocean steamer bound for
the tropics. As darkness comes on I've begin
to study the consultations that some friend at
our elbow is ready 10 point out to US, he said.
1--WE notice some star twnkling near the Lori-
zon, just making its daily circle around the
unmoying pole star above, one of the seven
stars Of the dipper. Let US note carefully the
relation of that star to the horizon and to the
stars of the surrounding heavens. We have
only to take out our watch and make a note of
the time. and our astronomical work may be
laid aside for the evening. Tomorrow night
let us come out on deck at the same time and
look at the star in its relation to the pole star
and horizon before. But the dipper that
was yesterday on the sea line has almost dis
appeared below the line. Last night the wake
OF the ship was pointed toward yonder ssar
and now it is a good deal above it. although
our direction has not changed. We are still
going south, but south now is not the same as
south then New stars have arisen on the
horizon as others have descended into the sea-
At last we reach the equator and we find The
pole star itself has sunk down to the horizon
We see no pole star IN the south, but as cur
studies on previous occasion have led us to
expect, there Is a spot. unmarked by any espe-
clally brilliant orb, around which the stars of
the southern heavens circle. There is no ex-
PLANTATION for this, except that we are not trav-
eilng over a level surface but over a curved
one. III We compare the sections of sky that
appear IN the south or disappear in the north
with the number of miles passed over by our
ships log shall find that they have always
been In proportion. We have then been sail
ing or steamlng over great circular arc in-
stead Of straight line, as it appeared to be-"
THERE ARE OTHER PROOFS
than these Of the circular character of the
earth. the lecturer said. We have only to look
out to when a ship is leaving port. 1t is
now Just on the horizon. and presently only the
masts are visible asd the hull is seeminly under
water. Something has interviewed between the
vessel and, the eye. What can this be but the
curved surface of the ocean?
A grander and more direct proof than any,
II we could only realize il. is that which we get
in ecipses of the moon Before an ecIipse be-
comes total watchers will see a curved line
which marks the edge of the shadow thrown
by the earth upon the lunar surface. and all
know that an object which always casts a reg
uiarly and uniformly curved shadow must be q
sphere.
THE AMOUNT OF CURvETURE.
The FIRST illustration though not so striking
as some others, Is the BEST for it shows not
only that the earth is round but also just what
the amount of its curveture Is Hence it is
found out what Its size is IS well its shape
One days voyage on the southwark bounG
steamer brings the star which was seen the
night before just appearing above the southern
horizon good distance above the waters edge
How many such lifts would be required to
bring II up to the zenith right over our headsY |
suppose we though that fifteen would be |
needed III then we could keep ON for Is DAYS |
II would be in the zenith, in 80 days it would be
there behind na IN would no 1ouyp hal |
the horizon, directly under our feet and in 60 |
days II would be IN the same place again where |
~ Is at present. In other words, We would in |
90 days have returned to just where We are |
now. Our log tells We have travelled 400 |
miles each day. and 90 times that would be |
$4,000 miles. This then is the circumference |
OF the globe" |
There is still, the lecturer said, a more accu-
rate method than that which he described By |
making observations with delicate instruments |
upon the land, instead of with the log, which |
Is so inaccurate, II has been possible to measure
accurately the of the meridian and the |
true circumference of the earth has thus been |
ascertained
THE SCIENTIFIC DEMONSTRATION.
The lecturer referred to the peculiarities Of
the earth's shape and its hattening in the re-
gion of the poles, and then proceeded to give |
the scientific demonstration of the fact that |
the apparent motion of the heavens is really |
caused by the motion of the earth itself Ex-
periments show a dIminution in the weight of |
objects as We approach the equator. which |
shows that the equator is really in motion A
portion OF this dImunition, however, can be &C |
counted for by the slight difference in the ro- |
tundIty Of the earth at the equator and toward |
the poles; and to infer from 1t the earths mo- |
ton It Is necessary to assume the nearly uni |
form density of the globe.
The lecture next Friday afternoon will con-
sist of an explanation of the methods by which 1
the distance OF the sun and other heavenly |
bodies has been ascertained and description |
OF the wonderful revelations which the tele- |
scope has given US regarding the physical con- |
stitutlon OF the SUM- 1t Is expected to have |
this and the future lectures of the course illus
trated by lantern views taken from the most |
distinguished authorities.
Hunting Evidence Against ParneH