The sun. [volume] (New York [N.Y.]) 1833-1916, 1906-09-24

WON IN Ntne1senrN Centur

What, then, do those various instances
indicated Surely very clearly that the
nuclei Of comets are In gensral collection
or ~aRgreRations OF meteorites, which arr
easily broken up into smaller groups OF
gradually spread and dispersed along
comets path until It may at last happen
that the comet will Be wholly dIssipated
and be seen no more. In any case dynam-
ical considerations indicate that the
meteoritos must continue 20 travel very
nearly In the comets orbit.
This hypothesis Ia confirmed by cases In
which the nucleus In Ehe head Of q comet
has actually appeared 10 undergo division.
In the comet Of 1913 It u recorded that the
head wa ut FIRST hks Q planetary disk, but
presently the astronomer Cysatus saw 10 % q
clustering group Of starry points. The CON-
eta Of 0linda IN 1880 and Of Brooks In 1850
broke into two parts, somewhat a did
Biela's. The nuclsus Of the great comet
OF 1882 gradually broke into four portions,
each OF which It Is quito conceivable may
some day form . separate comet.
But II maj be asked: II comets are thus
composed Of aggreGAtions Of meteorites,
OF stSe may We suppose the meteOrites
20 bef IN nswer 10 that their sise will
probably correspond with that Of such
meteorites " the earth In constantly en-
countering. These frequently fall upon Il,
being sometimes Of q few pounds In weight
or occasionally attaining even to hundred
weights or tons, as 10 indicated by speci-
mems found in sifa In certain localities, al
though they may not actually have boon
seen to fall. But II ID likely that the weight
OF by far the greater number may attain
10 only q grain or two, a. is the case with
moet Of those which traverse the earths
atmosphere in the form Of shooting stars.
A comets nucleus Is therefore probably
composed chiefly Of stony fragments vary
ing In si7e from that OF the finest dust to
that Of rocks OF considerable maGnitude.
At the same time portions OF Q more or less
metallic composition may be interrningled.
Eruptions from the nucleus may take
place in any direction. But they occur,
o might DO expected, most frequently
toward the sun, because on that side most
heat 10 received. Whsn 90 erupted the
matter sent forth d In general seen 10 be
presently thrown back again In . curved
path past the nucieus, 50 a to form
. brilliant hollow envelope around IL,
Tho nucleus being within that part Of
tho envelope which II most curved and
convex toward the sun. Several such
envelopes, outlying each other, are some
times seen, which have been formed In
succession from a series OF explosions, the
matter projected having attained 20 DIFF
ferent elevations above the nucleus before
being turned back.
These envelopes, produced In this way
from Jets first Of all emitted toward the
Gun, Of course help TO form the comets
tail after they have passed back beyond the
head. A much smaller amount Of elected
matter, probably OF q different kind, IN
sometimes seen on the sunward side OF the
head, like q tail pointing toward tho sum-,
and has occasionally beer termed the
comets beard. But the tail proper, fire.
quently Of immense extension and always
Of almost inoonoeivably light density, In
variably points away from the SUM- 90
IL even travels, in q sense, In front Of
the comet after the perihslion passage has
taken place and the comet has begun to
recede from the sun again.
All this very clearly indicates, a. nearly
all astronomers have long allowed, thai
some great repulsive force emanates from
the sun, which drives away with enormous
speed In the opposite direction any mat
ter elected toward the sun from the comets
after IL has risen 10 a certain
elevation; while the came force, II such
is elected in any other direction from
the nucleus, sooner or later turns It all, In
manner, backward into the tail.