Dodge City times., 1881-07-21

stellar aspect 1ne least diameter de-
termined at such times may be larger
than the actual Que. but cannot be
smaller. From the combination of mass
and diameter, the density of the nu-
cleus can be computed. In the case OF
Donati's comet, the diameter of the nu-
cleus was perhaps not more than hun
dred miles, while the height of the at
mosphere extended to eighteen thou
sand miles. You NAV be surprised to
learn that the corresponding density
of the nucleus was at least equal to
that of iron. What an unexpected
contrast is here presented to the prev
alent notions concerning the sun and
the comets, The solid sun is reduced
by science to the state of gas. while the
substance of the ethereal comet is SOL
id and heavy metal.
In its approach to the sun, the sur
face OF the nucleus is rapidly heated; it
is melted and vaporized and subjected
to frequent explosions; the vapor rises
in its atmosphere with wei defined
upper surface, which is known to OBJ
servers as an envelope. Various envel
opes, including each other, are often
observed.
The electriication Of the cometary
mist is analogous to that OF our own
thundercloud. Any portion OF the
coma which has received the opposite
kind OF electricity to the sun and to
the repellei tail will be attracted. This
gives simple explanation of the mega
tive tails which have been sometimes
seen, directed toward the sun. In cases
of violent explosion, the whole nu-
cleus might be broken TO pieces, and
the coma dashed around so as to give
varieties of tail, and even multiple
tais.
The relations of the comets to the
solar system present an interesting and
instructive study. With very few ex-
ceptions. their visible paths are so near
ly parabolic. and the positions of their
nuclei and centers of gravity so uncer-
tain in the midst of their come, that it
is quite out OF the question to obtain
nice enough data TO measure exactly
the extent of their orbits. and ascertain
how great may be their deyiations from
exact parabolas. and whether the devil
atoms are such as to make them ellipses
or hyperbolas. If an orbit is actually
parabolic or hyperbolic. and if there is
no decrease in the central attractive
force as the comet approaches the sun.
it must have entered the solar system
from outer space, and cannot be one of
our permanent partners. 1t will leave
the system again, and We may never
expect its return; unless, indeed. hav-
ing passed through the circuit of other
suns, after myriads of years. it reap
pears in an orbit entirely different from
its former one. so rs to afford no evil
dence through which it may be recoy-
nized. But ifit moves in an ellipse. and
does not leave our system, it will return
in sensibly unchanged orbit. through
which it may be detected"
The astronomer is often asked. upon
the announcement of a comet, els it
new one?" and the tone of the inquiry
usually implies feeling of satisfaction
in witnessing the discovery of new
star. But it is just the reverse with the
astronomer himself. He ransacks the
records, hoping against hope that he
may enjoy the good fortune of ascer-
tanning that the new comet is an old one
old, at least. in the sense that it has
been observed once before, but not
twice. On its first temperance
comet is certain to be loaded with the
name of the geometric discoverer of its
path. Its theory is computed; its future
returns are rigidly predicted; its social
position is definitely established. and it
takes its place among the registered
members OF our constellation. But
comet NAV belong to our system. and
yet go SO far from the sun that the in
tervals between its periods Of visibility
may be as long as three hundred thou
sand centuries.
There are few comets of WHICH the
character is evident at
once. Their orbits are decidedly elliptic
al: their neriOds do not exceed a baker |