Milford chronicle., 1895-02-22
ENcKe S COMET.
This wisp Of Nebuiosity Is Due ct It's Peri.
helion Point

This Wisp Of Nebulosity Is Due 1t It's Peri,
heIion Point
Encke's comet is returning to perihe-
lion. It was discovered en- Nov travel
ing toward the sun in the constellation
| Aquarius. A telescope is needed TO see it.
| When seen, it appears as a mere wisp OF
nebulosity, and at its brightest it win
hardly be visible to the naked eye, yet its
return is an event Of high importance TO
astronomers, and through astronomers to
the advance of human knowledge.
1t is due at its perihelion point on Feb
/ (, after which 1t will retreat into space
again. At every step in its progress until
/ 1t has turned the goal and faded into the
| distance it will be closely watched, its
gait will be measured, its peouliarities
will be noted and as far as the astrono-
mers are concerned the earth will become
kind of judges stand where necks are
oraned and eyes are strained and fractions
OF a second loom gigantic as the little
courser stretches for the wire.
The extraordinary interest in this return
of Enoke's comet arises from two sources.
In the first place, the comet began many
years ago to exhibit a marked popularity
in its rate of motion. Its period from one
perihelion passage to the next is about 4
years, but this period has been slightly
and gradually shortening ever since the
discovery Of the comet in 1883 Up to 1868
the rate of shortening was about = hours
on each revolution, and the conclusion
was that the comet suffered a resistance
from some medium pervading the space
through which it travelled. The first re-
suit of such a resistance would be to re-
tard the comets advance in its orbit and
foroe-it little closer to the sun. But be-
ing nearer the sun it would necessarily
move faster and thus would arrive at each
return a trifle earlier at perihelion. As
tronomers had hardly begun to attack the
problems arising out Of the existence of a
resisting medium in space, which the mo-
ton of Encke's comet seemed to demon
strate before a surprising change occurred
in the rate at which the comet quickened
Its speed. This change was first noticed
in 1868, at which time the comets accel-
GRAFTON fell of to about one-half its for
mer amount, and the new rate has been
maintained ever since.
Such an alteration Of rate is ineonsist- |
ent with the idea of O general resisting |
medium occupying space, but there is no |
lodging the fact that something inter- !
feres with the motion Of Enoke's comet |
Two suggestions have been made. One, |
due to Professor Young, is that Of a regu-
larly recurring encounter Of the comet |
with cloud Of meteorio matter; the other
put forth by Mr. W. 7. Lynn, is that the
attraction of the asteroids, near whose
thronging orbits the comet passes when
most distant from the sun, may be the
source Of disturbance
If Enoke's comet were a massive body,
these effects would not be noticed 1t is
because the comet is SO insignificant
mote, flying like an airy spirit among the
planets that it is able to tell us some
thing Of subtle forces and resistances
which the ponderous earth would ride
down unnotioed
The second reason for the particular in.
.erest awakened by this return Of the
,omet is that on its last previous visit to
The sun, in 1891, it passed comparatively
Alone to the planet Mercury. The effect
# that approach must manifest itself also
n the comets motion. The great Jupiter
s accustomed to send comets hither and
hither at his will when they get within
lis sphere Of attraction. Mercury cannot
10 that, both because it is much smaller
han Jupiter and because it is in the i'm
mediate presence Of the dominating sun,
ut its attraction is sufficient neverthe. \
-77f W ~oNso a ES1SeP PpAuAe CuduBb III bne
omet's orbit. Now, this change is a meas
re Of the attractive power, or mass, Of
be planet producing it. It viii therefore
i've clew to the mass Of Mercury, con
erning which astronomers are still more
r less in doubt. The mass Of Mercury
eing ascertained, other related facts are
aimed for science, and thus little wan
ering comet which, If it could be captur- Z
] and condensed into a solid form, might
OF be the largest exhibit In meteorolog-
al museum, proves to be an explorer Of
lterplanetary space, each Of whose jour
ays into the unknown brings enrichment r
knowledge to man.--Garrett P. Serviss L
New York Sun.