JS12.] jf/r. on the Comet, its Train, Kc. 
atmospheres from our’s is considered, 
and how far they are above our’s. 
The form of the cometary train (which 
is paraboloid like its orbit) seems to be 
very justly ascribed to the peculiar di¬ 
rection of its motion.* It is also ob¬ 
servable, that it winds before, below, 
and behind, the star, in a turbinated 
wreath, and has generally been con¬ 
spicuous Very much below the star; so 
smich as, according to its distance, might 
^imount to 4 or 500,000 miles. 
It seems therefore to be repelled by 
the impulse of the sun^s rays (similar 
electricities repel each other),—and to be 
thrown back from the comet, in a direc¬ 
tion nearly, but not precisely, nor at all 
times equally, opposite to the sun. 
The curvature of the train has been 
very remarkable during great part of its 
appearance. And this has been always 
concave on the same side, the receding 
side of its path ; and convex on the other, 
that side which is nearest to the path 
toward which tlie comet is moving. This 
curvature, as the motion becomes slower 
a^id more equable, has nearly vanished. 
The obliquity of the train, as the comet 
moves in its orbit, by which great part 
of one branch is now nearly thrown into 
profile, is also observable. 
The great divergency of this vast pencil 
of light, which for some vveeks was eight 
or ten millions of miles wide at the far¬ 
ther extremity, and sometimes less than 
half a million nearest the nucleus, and 
above 30 m'.llions of miles long, is also 
worthy of notice. 
This exceeding divergency seems now 
much diminished. 
d he" darkish shadow, as it appears, 
running quite down to the nucleus, and 
tliverging to the farther extremity, is also 
remarkable. 
It cannot be shadow, for then it would 
come or go as it receded: it is not smoke, 
for the fixed stars are distinctly seen 
through it. It appears to be a mere 
void space and absence of light. It was 
first apparent at the farther extremity, 
(6 S.) but the next night (and uniformly 
since) through the whole extent. 
I can by no means revive the old 
hypothesis, and ascribe It to the rays of 
4he sun passing through the atmosphere 
of the comer, as through a lens. This 
might consist w>ith the curvature, which, 
how-ever, is better explained by the re¬ 
moter part of the train as it ascends, not 
* Gregorii Astronomia. 
Mojjthly 221, 
^47 
keeping exact pace with the nearer, 
which is the Newtonian solution. 
It will not consist with the vast dis¬ 
tance of the comet all along from tlie 
sun and the earth. 
It will hardly consist w-ith the narrow¬ 
ness of the pencil of rays next the nu¬ 
cleus, and its great breadth at the farther 
extremity; some convergency at least, I 
think, ought to have appeared. 
It ill consists with the total absence 
of that prismatic light which accom¬ 
panies refraction. 
It consists with the train of this 
comet, worse than tliat of others; be¬ 
ing still visible when it makes so con¬ 
siderable an angle with the earth and 
sun. 
It least of all consists with its being 
seen unequally diffused round it, when 
in conjunction with the sun, and with 
its being seen since so far below the 
nucleus. 
But, if the atmosphere of the comet 
be considered as in a moderate state of 
electric excitement (I mean by mod€<^ 
ratey much short of ignition and combus¬ 
tion), the phcenomenon will agree with 
the cause assigned; especially if some 
part of the solar atmosphere be supposed 
to have been absorbed by the comet, in 
passing its perihelion, to the idea of the 
train being formed by the rays of the 
sun passing as through a lens, ' 
I have made the experiment very 
fairly : the curvature may be in some 
degree imitated by transmitting the rays 
of the sun through a rather large Jens, of 
about six inches focus, held very ob¬ 
liquely to the sun and the paper. But a 
false hypothesis will account for one or 
more phenomena; while no hypotlie- 
sib can be true which is contradicted by 
any. 
I would observe, that the head, in¬ 
cluding the brightest part, of the coma, 
appears of a greater diameter and denser 
light; although the comet now re¬ 
cedes both from the sun and earth. 
This is obviously inconsistent with its 
being the sun’s rays transmitted througl^ 
the head of the comer, as through a 
lens: but it is perfectly consistent with 
the hypothesis, that tlve luminous atmo¬ 
sphere subsides and condenses on the 
comet, as it recedes from the sun. 
I have now, from 32' p. 5 to 7, ' 
viewed the comet with my night-glass, 
and the excellent reflector of Dol- 
lond ; and wiih'Gilbert^s telescope, (best 
improved) lent me by the Rev, Mr. 
4 A Lothbury 
