The Republican. [volume] (Oakland, Md.) 1877-current, 1882-11-11
COMETS.
Prof. PrOctOr's Views About Comets
and Eheir PecuIIarities.

prof. PrOctOr'S Views About Comets
and Their PecuIIarities.
To the Editor Of the NeU York Herald:
During the last two years many comets,
some of them bright ones, have been
seen, and from all sides the question
reaches me, Do we know more about
comets than we did two years ago? L
Wlsh that | could honestly answer, We
know a great deal more; but cannot.
Still, something has been added to our
knowledge, and, unless l mistake, al
though that something may in itself be
slight, the manner in which it has been
learned is such that the small modicum
of new truth is full of promise.
| suppose every one who reads these
lines knows pretty well what are now
the chief difficulties in cometic science.
We want to know why, as the comet ap-
proaches the sun, it throws out all around
it, but chiefly toward the sun, the lum-
nous appendage we call the coma or
hair-really, so far as we can Judge, a
nebulous or gaseous envelope. We
want next to know why the matter thus
thrown out seems to become subject to q
repusive force by which it is strongly
driven from the sun to form what is
called the comets tail. We want to
know how much of the light of the COM
cts nucleus Cor brightest part,) coma or
nebulous surrounding, and tail is due to
the mere reflection of sunlight and how
much is inherent. Also, having ascer-
tanned beyond all possibility of doubt or
cavil that part of the light, in all three
cases is inherent, we want to know how
sufficient heat is acquired to raise
nucleus, coma and tail to actual inner
ent luminosity.
Now in former years, and especially
during the appearance of the comets of
Wnnecke and Brorsen, in 1868, astrono-
mers recognized that part of the light
of some comets, at any rate, is due to
the inherent luminosity of certain COM
pounds of carbon and hydrogen. DIR.
William Higgins, of London, is not
very daring scientific Spectator; he
usually errS on the side of excessive eau
ton Gndced have myself been stating
respecting his results for the last fourteen
years, what he now only begins to state
for himself) therefore, when he does
speak positively we may believe that he
Ms found the evidence overwhelmingly
Srong Well, he says in lecture very
recently delivered before the Royal In
Nltutlon: 1.-The general close agreement
in the case of some twenty comets of the
bright bands in the cometary light with
those seen in the spectra of hydrocarbons
justities us fully in ascribng the light of
these comets to matter which contains
carbon in combination with hydrogen"
Until quite recently this has been the
lNr ,,,,l,l /, l. I
Ognized by the spectroscopic method as
forming part of the substance of comets
And the wonder has been that substance
so refractory as carbon-a substance
which cannot be vaporized in our labor
atories under any ordinary conditions
should thus appear in the form of lumin-
Gus vapor in the case of comets further
from the sun than our own earth. 1t is
difficult to see where the heat can come
from by which the carbon present in
these bodies can thus give light-evidence
(Which means also heat-evidence) of it's
presence. 1t is not carbon only which
is thus shown to be present, nor even
carbon and hydrogen only; nitrogen
seems also to be indicated Professors
Liveng and Dewar have found that GER
=
spectra of certain compounds of carbon
when nitrogen is also present, and that
intact they indicate the presence of cyan
ogen, well-known nitrogen compound
OF carbon. Now these bright lines have
not only been SEEM they have been pho
tographed in the spectrum of the bright
est comet of 1881 (by DR.. William Hug
gnsn London, and by DR.. Henry Draper
IN New York;. A part, then, of the
night OF every comet is inherent, and
comes from luminous mixture of car
Oon' hydrogen, nitrogen and probably
oxygen also. A part of the light, is,
however, reflected sunlight, nearly the
Whole of the tails light being thus re-
Hecied and a great portion of the light
VI the coma, with smaller portion of
.ne light of the nucleus. Even
mere, however, we cannot De as
Sured that all the light which might be
rejected sunlight is really so. The only
way in which we can distinguish such
Ight from inherent light coming from
glowing solid or liquid matter, is by
noung that when we analyze reflected
sunlight certain tints thousands of them)
aie missing, so that across the rainbow
united streak, into which the spectre
scope resolves such light, there are seen
numbers Of dark lines corresponding to
sllose missing tints. In the case of light
from seh-luminous solid or liquid mass
no such dark lines are seen. But the
laht light of a comet is not very easily
ahalyzed as closely as is necessary to
snow whether these dark lines exist in it
III not Until quite recently astronomers
Ia nave been contentto regard the presence
vi continuous rainbow-tinted spectrum,
WIN or without lines, as evidence that
NE comet shone by reflected sunlight
wv however, q closer scrutiny has
peen made, and in the spectrum Of the
brightest comet of 1881 physicists have
succeeded in detecting the dark lines
Wne So-called Fraunhofer lines) of the
Iolar spectrum. These lines have even
So Photographed by DIR. Higgins (they
"on ! show in DR., II. Diapers photo
EsgaphS Now, failing to obtain or see
s Snese dark lines means little or nothing;
''Ving them, however, and, still more,