The farmer and mechanic. [volume] (Raleigh, N.C.) 18??-19??, 1910-05-03

us tail. IS estimated at - MAJ
= me ar at the earth's surface ~
aieSs vacuum produced in ~ I
a.orS Is solid milestone 30 -
.Is' ihoeed, Il has been said tho. -
alH@rS ~teieseopic comet tf1v or
q nuIioTed thousand miles in diaue+ar
coulo De brought into a lahor.tn.'
couid De condensed and nacled -
III d PHI box. The tail Of . coras :,
40 ieat llothlng as the human MIND
sdh possibly imagine. The earth has
ispea'eoiS passed through tails Of
b1r ,t roe "lthout being p~ercepti-
pis Influenced. A further proof Of tho
Die tenuity OF comets -
shoWn by the fact that even the fool
lest rays OF light have been ohserv-ad
70 easerse with impunity some hun
- u thousands of miles Of their
substance, even where it was anna
Tently most dense. Stars We've nla;nIr
visible through the very center nf III
iey comet in 1885. Again. the bod
or Encke's comet of 1898, as il neared
the sun, contracted from a diameter
oI -oi'ooe miles on October 9, to one
O. ohiy '.oeo miles on December II.
Sucn an enormous which
IS peculiar to comets, can be possible
ohlS IN very attenuated bodies.
me volatility of conetary matter.
as Well as the disintegration of ON
cts, VIII appear evident when the de-
velopment of their tails is explained.
the striking popularity OF the tails
OF all comets is that they are turned
away from the sun as though acted
upon by some repelling force. Several
genlo theories attempt to explain
the nature of this repulSion. The cleo
trical theory, first suggested by Oibers
in 1912, holds that the repulsion Is
electrical. 1t assumes that, since a
body subjected TO ultraviolet light viii
- V nj ~ 01f yEynl
the ultraviolet rays from the sun will
drive of negatively charged particles
from a comet, which is >ysumed to be
1tnout an electrical charge. The neg
atfye charge ON the sun Will then repel
these similarly charged particles and a
tail will be formed. The remainder,
and by far the larger portion, Of the
comet Will be positively charged and
consequently Will be attracted by the
suns negative charge. The light
pressure theory as suggested by Ar
rhenius embodies the principles of
MaxWeIIs electromagnetic hypothes is,
which holds that light exerts 81 pres
sure upon bodies proportional to the
light energy in a unit of space. Ac-
cording to Arrhenius, the violent mo
tons and collisions in the head of a
comet break up the sofid parts into
minute particles which are driven
away into a tail by the light pres
sure rom the sun.
" hatever may be the nature OF the
repelling force, it is certain that par
tieles are driven Out from the head Of
the comet in x direction opposite the
sun. and that this process becomes
moro rapid the closer the comet APP
proacheS him. No tail at all is visi-
bic when the comet first appears from
the abyss of space. Soon. however,
the Telescope reveals masses Of vapor
i ri-in0 FROM ire head than
spreading out behind III the form OF a
tail. The nearer the comet approach
es the sun. and the greater the heat
to which it IS exposed, the more rap
idly the volatile matter escapes in
vapor and streams away into the heav-
ems. On passing the sun It emerses
on the other side with increased bril-
lance and a tail of ereater length
pointing in q direction opposite tina
il held before. Thu the comet ap-
pears to back out of the solar Sys-
tenn.
The foregoing facts show that the
matter in the comet is volatile, ana
that the tail is an not an
appendage. This being SO, it is obvt-
Gus that the comet disintegrates and
disa in proportion as its matter
is voIatilized and elected into the tail,
and it must also appear thinner ana
DINNER at each visit TO our SKIES.
Hence comets of short periods will dis
integrate more rapidly than those OF
long ones, because their matter Is
more often subjected to the volatillz-
ing heat OF the sun. 1t deserves TO be
noted that a few comets run SO close
to the sun that they are torn to pieces
bv the tidal influence of his Temend-
Gus s~ravitation. Biela's comet was dls-
in~tegrated in this way, ana is no"
supplanted by the stream or Bieiio
meteors following in its former orbit.
The Great Comet of 1882, also, went
to pieces before our very yes from
the same cause.
T, is now necessary to consider the
Questions arising with reference to the
occurrence of com ets-Such questions
as those Of their origin, orbits, periods'
and velocities.
h origin of comets IS a matter OF
-a-4rororru cnanng nOnleFS. Some