Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1898-12-04

distance Of one member Of the solar sys-
tenn is determined those Of all the
others can be calculated from the rela-
lions which the law Of gravitation re-
veals 10 us. 1t is matter of import
ance, therefore, 10 continue the work OF
discovery, since we may at any time
come across an interesting or useful mem
Der of the family, and that we may be
able TO distinguish between minor planets
already discovered and new ones, their
orbits must be determined as they are
discovered, and some sort Of watch Kept
on their movements.
The most ordinary way Of observing
comet with an equatorial Is as follows:
Two bars are placed in the eye-piece OF
the telescope at right angles 10 each
other, and at an angle OF forty-hve de-
grees to the direction of the apparent
daily motion Of the stars. The telescope
is turned 10 the neighborhood OF the
comet. and moved about until it is de-
tected The telescope is then put little
in front Of the comet and very firmly
fixed. The observer soon sees the comet
entering his field, and by pressing the
contact button he telegraphs TO the chron-
graph the time when the comet is exactly
bisected by each Of the bars successive
". He then waits until bright star, or
il may be two or three, have entered the
telescope and been observed in Ike man
ner. The telescope is then unchanged,
and moved forward until 1t Is again
ahead Of the comet, and the observations
are repeated. and this is done as often
as Is thought desirable. The places OF
the stars have, Of course, TO be found out
from catalogues, or have TO be observed
with the transit circle, but when they are
known, the position Of the comet or minor
planet can easily be inferred.
IL is only recently that Greenwich has
taken any great part in this work. In
the main, double star astronomy has been
I'm the hands Of amateurs, at least in Eng
land. But the discovery in recent years
of many pairs so close that a telescope
Of the largest size is required for their
| successful observation has put an import
ant section of double stars beyond the
I reach of most private observers, and
therefore the great telescope at Green
witch is now mainly devoted to their
study
There is a striking contrast between
the great telescope and all the massive
/ machinery for its direction and move
| ment and the objects on which 1t is d.
rected-two little points OF light separated
| by a delicate hair Of darkness.
| The observation is very unlike those
| of which we have hitherto spoken. The
, object is not to ascertain the actual po-
| sition in the sky of the two stars, but
| their relative position TO each other. A
! SPIDERS thread of the finest strands Is
/ moved from one star to the other by
turning an exqustely fine screw; this
! enables us to measure their distance
| apart. Another spider thread at right
angles 10 the first is laid through the GEN.
tres Of both stars. and a divided circle
! enables us to read the angle which this
| line makes to the true east and west di-
rection. Such observations repeated
year after year on many stars have en-
abIed the orbits of not a few TO be laid
| down with remarkable precisions, and We
! find that their movements are complete
| " consistent with the law Of gravita-
ton.
Further, just as Neptune was prerecog-
nized and discovered from noting the ir-
regularities in the motion of Uranus, SO
the disturbances in the place of Sirius
led to the belief that IL was attracted by
a then unseen companion-a companion
! whose position with respect to the bright
| er star was predicted and afterwards
| seen.
]
/ the Bond Of Universe. yet it leaves US
with several weighty problems The OBJ
servation Of the positions OF stars shows
that though we call them fixed they real
ly have motions of their own. OF these
motions, a great part consists Of a drift
away from one portion of the heavens
towards a point diametrically opposite 10
/ ii, a drift such a must be due, not TO q
| true motion Of the individual stars, bu1
to a motion through space Of our sun
and It's attendant system The elder
Hersche was the first to discover this
! mysterious solar motion. Sir George Airy
and Mr.. Edwin Dunkin. for forty-si>
years a member of the Greenwich stan
and from 1SSl-si the Chief Assistant, sew
orally contributed important determine
tons of its direction.
What is the cause OF this motion, wha
| is the law of this motion, is at present
beyond our power TO find out. Many
| wears ago a German astronomer made
the random suggestion that possible VIZ
were revolving in an orbit round th'
! Pleiades as centre. The suggestion
was entirely baseless. but unfortunate
w has found its way into many popular
works. and still sometimes Is brought
| forward as II it. were one OF the estab
|
the present time only say that this iso
lar motion is a mystery.
There is a greater mystery still. The
stars have their own individual motions
and in the case OF a few these are the
most amazing swiftness. The earth II
its motion round the sun travels nearl,
nineteen miles in a second, say one thou
sand times faster than the quickest
/, rush OF an express train. The suns
| rate of motion is probably not quite 81
swift. but Arcturus. sun far larger thar
! our own. has a pace some twenty times
as swift as the orbital motion or thu
earth. This is not motion that w
/ can conceive of as being brought abou
| by gravitation. for II there were scm'
unseen body so vast as to draw Areturu:
with this swiftness, other stars too woult
be hurting across the sky as quickly. Lik
Job OF old we are speeches. when tn,
question comes to us from Heaven
"Canst thou guide Aroturus and hi
| sons?''
| n WAITER MAIyNDER +. r.. A. s.