960 CO” _ The Great Comet of 1861. 
The following, companies by Mr. Hall for Washington mean 
midnight, will give an idea of the path of the comet previous 
to its becoming oN in the northern hemisphere. 
W. m log. 4 
June 12°5, 61° 391 — 26° 32/3 9°7222 
' 3.16°3 23218 <4 9°6182 
20°5, 66 4°9 17 31% 9°4831 
24°5, 71 56°9 — 3 45°4 9°3105 
, 85 17°9 +27 41:5 9°1420 
July 2°5, dp2..15.°9 63 34:0 9°2027 
a 188 53°9 64 38°6 9°3884 
‘ 207 50°1 +58 56°5 9°5420 
June 29°0, 89 30°4 +33 8°4 9°1330 
The comet passed its ascending node June 28086, Washing- 
ton m.t., when the difference between the heliocentric longitude 
— 
of the comet and of the earth was 2°0/. The difference be- 
tween the geocentric ‘ona of the comet and of the sun was 
12° 29’. Log. of distance of the comet from the earth =9:1529, 
Calling its Gases unity on July 2°5, we have 
June 12°5, Brillianey = 0°11 
16° 018 
5, 
20°5, 0°33 
245, 0°69 
28:5, 141 
July 25, 1:00 
65, 0:50 
10°5, 0-18 
computed by the equation, brilliancy = _ _! 
It will be seen that the comet, at about the time of its peri- 
helion, must have been well situated for observation at the yee 
of Good Hope and other points in southern latitudes. The 
culated brilliancy is indeed much less than on the 2d of July, 
being only about one-tenth—but it is well known that the form- 
ula cannot be relied upon for the variations of the light of aie 
which is greatly influenced by their positions relatively to 
perihelia. 
It is probable that at least the head of the comet was much 
brighter at the middle of June than it was after the first of July, 
southern observatories, especially from the Cape of Good Hope, 
which has often, in similar emergencies, proved itself the most 
important astronomical position occupied by any existing ob 
servatory 
ont the above elements, the diameter of a nucleus may be 
variously estimated at from one hundred an three 
from - 
