The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1872-08-03
The Nature of Comets.

comets, makes It ms purpose 10 expllin
the remarkable phenomena they prescott
by an application Of the established
principles Of physical science alone.
lie starts from the fact that water,
mercury, aud many other substances,
eve1 solids undergo evaporation to a
certain extent and he iulers from the
ordors Of the metals that they also,
even at very low temperatures, are con.
stantly giving of vapor, though 10 an
iuapprecably small amount; from whish
he concludes that mass of matter 10
space win ultimately surround itself
with its own exbalations, the tension Of
which will depend upon the grayitatiye
energy Of the mass and the existing
temperature, If the attractive force Of
the body be insufficient 10 give the
surrounding yapor its maximum tension
FOR the temperature, the evolution Of
yapor will so on until the entire mass
is converted into it. A further anaIyti.
cal inquiry leads to the rcsplt ihsl
fuite mass Of gas in unlimited space is
in condition Of unstable equilibrium,
and must become dissipated by continual
expansion and a consequent decrease Of
density; and necessary consequence Of
this result is that the space contained
in tie stellnr uniyeres must be filed
with matter 10 the from Of gas.
BY assuming, for the purposes of
calculation, that stellar space is every
where filled with atmospheric air, and
taking the temperature as that of melt
ing ice, he finds that gas ia space, at
It's lower limit Of density, is so altenua-
TED that a mass of air, which on the
earth's surface would occupy volume
Of one cubic decimeter, would, when
reduced to this density, fll sphere of
inconceivable dimensions; a ray Of light
would not traverse its radius in a less
number OF years than is expressed by
the numeral one followed by ninety.
eight ciphcrs. Such medium could
have no appreeable effect either upon
rays Of light or the motion Of bodies.
Solid bodies in space must, by virtue
Of their attractive force, condeuse the
gas SO as to form an atmosphere on
their surfaces, and the density Of the
envelopes can be calculated when their
size aud mass are known. The value
found for the moon is vanishing
quantity, and perfectly in accordance
with the fact that no lunar atmosphere
has ever been detected For the larger
! planets, however, the value is very
/ great, aud the high density of their
atmospheres must occasion perccptable
effects upon the light reflected by them.
The temperature Of fluid mass,
existing far from the sun or any body
capable Of radiatiog heat to it, would
be that Of the surrounding space, and
If its attraction were not too great slow
evaporation would convert it into
sphere Of vapor. Should it, on the
contrary approach the SUI, the heat
would cause the whole to be yaporized
in much shorter time than in the
former case, and the smaller the mass
the shorter the time would bc. The
smaller comets, which often appear like
spherical masses Of yapor, are ex implies
Of bodies Of such nature.
The self.luminosity Of comets he
sets down to electrical excitement; aud
if it be granted that electricity may be
developed By the action Of solar heat,
in the process of evaporation or the
mechanical aud molecular disturbances
arising from it, VIC have cause sulH-
cient to account, not ouly for their
self luminosity, but also for the forma-
tiou Of their trains.
He then proceeds to discuss the
quantitative difference 10 the effect OF
grayitative aud electrical forces upon
masses at distance, and shows that,
when body is under both influences
simultaneously, an increase Of the mass
results in a preponderance of grayita-
tion, and sufficient decrease Of the
same, in preponderance Of the electri-
cal action Hence the nuclei Of comets,
as masses, are subject to grayitation,
while the vapors developed from them,
which consist Of very small PARTICLES,
| yield to the action of the free electrici-
ty of the sun Careful inycsticat;on
shows that sunnos;ng tLe Frse eloe,r;e;
! tv of the sro 10 be no greater tban bas
been repeatedly observed on the Earth's
to snbere n miiIimcters i d;ame,er
and 1o0 Of p,ilI;crom il we;rLt a
velocity Of over 40s ooogranhicai miIes