, 1861-07-19
THE GREAT COMET OF 1861.
BIZ PROF. o. II. MITCHELL.

which was generally observed throughout
the United States and in Europe. Owing
to the position occupied by the Comet,
moving as it did in plane nearly peTpen-
dicular to the plane Of the ecliptic, and
not far from the pole of this same plane, it
was somewhat difficult to deduce from
the observations, very exact elements Of
the Comets orbit The longitude Of the
descending node, Tor point IN which the
Comet passed from the north to the south
side Of the ecliptic,) was we'll determined,
as we'll as the inclination OF the plane Of
the orbit. The time Of passing the perihe-
lien WAS fixed for about the Sd Of June,
1861. I say about the Sd, for compilers
difftred one OF even two days ia their re-
suits. All the observations were very
thoroughly discussed, and an eciptic or
bit was deduced, giving period Of revo-
luton Of more than eighteen hundred
wears.
An ephemeris vas computed, showing
the path of the comet among the fixed
stars, as seen from the earth in its retreat
from the sun, and Of course no astronomer
would look elsewhere tor the comet than
upon its predicted route. This predicted
route, for the months Of June, July and
August, was on the south side Of the plane
of the ecliptic, and the comet did not rise
sufficiently above the plane Of the horizon
in this latitude to be seen.
Such was the condition Of our knowl-
edge concerning the Thatcher Comet, when
brilliant object, with a magnificent train
Of nebulous light appeared suddenly in
the northern heavens. When its place was
compared with the computed place Of
Thatcher's Comet, the discrepancy was 80
large, nearly 90 deg. Of declination, that it
was at once taken Tor granted that the new
object was quite Independent Of any con-
nexion with the former Comet
From observations obtained on the even
ings Of July 2, 8 and 4, at Cambridge,
Messrs. Stafford and Hale computed ele-
ments, when it was discovered that the
orbit Of the stranger had an inclination to
the ecliptic nearly equal to that Of the
Thatcher Comet-that the perihelion pas
sage was seven or eight days later than
the former, and that the distance Of the
new object from the sun, wlea in perihe-
lio; was a1mos. identical with that of the
old. From these facts, it has been stated
in the public prints, 4 know not On what
authority that these objects were the same,
and that the discrepancies between the
elements might be reconciled, either by the
TACT that the Comet had been greatly dis
turbed by some planet in its approach to
the sup, or that the first set Of elements
were necessarily inaccurate, from the Pc
culiar position IN which the Comet was
seen st its first appearance.
From observations obtained at the OBJ
servatory on the evenings Of July Sd, 5th
and 9Th, Mr. g. ". Hough, Assistant, has
computed the following approximate Gle
menta Of the Genet now visible:
T%June II ,4SS5d Washington IL T.
t;=249 deg. % min.
0=278 deg. Al min.
%80 deg. IL min.
Log, g-9. 911 ,3446
july s. The Comet was observed at its
| lower elimination with the Olcott Meri-
dian Circle.
July 5. the Comets place was deduced
by comparison with No. 22785: Lalande
july 7. The comparison was No
1882: Arg. Zones. =.
Mr. Hough also computed the following
approximate clements Of Thatcher's Com
Ct, from Observations made at the Obser'
| vatory cn the evenings Of April 10Th, 14th
and 17th. 1861:
| 7-JuDe 8, ,560d.
'tI,-242 deg. IS min.
$50 deg. 80 min.
LIS deg. 40 min.
Log 90. 9845
4 comparison Of these two sells of ele
ments will show that the Thatcher Come
is not the object now visible in the heavens
Il is true that the value Of T {thc time 0
perihclion passage) differ only some eigh
dnys. That the angles Of inclination 4
differ less than eight deg; that the 1oga
rithms Of the perihelion distance are nearl,
alike, but the values of the longitude of thl
descending nodes are so entirely different
the planes in which the two Comets move
makc with each other an angle Of near],
sixty deg, and while they chnnced to COM
very near each other, In their nearest ap
preach to the sun, their paths among til
fixed sl8rB lie in regions Of the heaven
very remote from each other, except at tn
point where the orbits nearly intersec
each other, in the immediate vicinity Of tn
perihe!ion points.
On the evening of the Sd of July, whel
the Comet II was most brilliant, computa
ton shows it to have been at distanc
from the earth Of about nineteen million
Of miles. It Was already rapidly recedin,
from the earth, and On the evening of th
Th July, its distance had become twenty
seven millions ofmiles
| We must conclude TINT the present Wis
itor is q stranger, Of which we know onl
such facts as have been obtained since it
appearance and discovery on the 30th {
April, 1861:
| It is not the Comet sometimes name
after Charles Y. This Comet was first Of
served in 1864, and again In 1856, when
threw off train Of brilliant light one hu1
dred degrees in 'ength. These two Con
| atc oro nrac,1na cd II, ha the eama in nenp,