290 
[No. 3, 
The great Comet of 1861. 
We may .find the comet’s distance from the earth at any time, 
when we known 8, by the formula, true dist. = curtate dist. cos 
helioc. lat. 
Thus on the 5th 8 = 9 0657813 
cos b = 9.99285SO 
9.0729233 . - . true distance = .118283 
and .118283 X 95,000,000 = 11,237,000 miles, which sufficiently 
explains the length of the tail, and the rapidity of the motion. 
I have, in another place, expressed an opinion, which I still retain, 
though it has not been noticed (up to July 27th,) by any European 
astronomer, that the comet is identical with Mechain’s Comet of 1781 : 
and that therefore its path is an ellipse, with a period of about 
80 years. Mechain’s Elements for the comet of 1781, are 
Node, 
263° 
Inclin., 
81° 
P. Lons’ 
239° 
— Dist., 
775 
— Pass., 
July 7. 
Motion, 
Direct. 
Its near approach to the earth, and the great difficulty of computing 
the elements of a body, with an orbit nearly perpendicular to the 
ecliptic, will amply account for the discrepancies. There are indeed 
very considerable variations in the determinations of some astronomers 
at home, chiefly arising from an over anxiety to rush into print. 
There can he no doubt that the comet seen in the southern hemis- 
phere in June was our comet. When seen at sea, it was rushing 
northwards with prodigious velocity, after passing its perihelion on 
the 12th of June. It did not ascend to the north of the ecliptic 
until the 29th or 30th. * 
I suspect too that it is the same comet, which was seen in Europe 
and America in the end of April and May, of which Mi. Hind gives 
the following very rough elements : 
Node, 31° 
Inclin., 79° or 80° 
P. Long., 243 
— Dist., :. .92 
* If the gentleman who sow the comet had but measured its distance from 
two Btars, his observations would have been very valuable. 
