256 D. Kirkwood on the origin of the Comets of 1812, ete. 
The fourth comet of 1846 was discovered by DeVico, at the 
Collegio Romano, on the 20th of February, and continued visible 
about 10 weeks. The elements of these comets are as follows: 
Long. of! Long. of Perih. | Eccen- Direc-} Compu- 
Per. |Asc. Node.} Incl. | Dist. | tricity. | Period.) tion.} tor. 
Perihelion Passage. 
| y- 
253° 33’|\73° 57/10°7771/0-95454/79°68 | D |Encke. 
TT° 37/\85° 6710°6637/0-96224/73°715| D | Peirce. 
1812, Sept. 15d, Th.|92° 51’ 
1846, Mar. 5, 12,/90° 31’ 
The wonderful similarity of these elements, except in the lon- 
gitude of the ascending node, is at once apparent. It will also 
be noticed that the longitude of the descending node of the lat- 
ter is very nearly coincident with that of the ascending node of 
the former. These remarkable coincidences are presented to 
the eye in the following diagram, where the dotted ellipse rep- 
resents the orbit of the comet of 1812, and the continuous curve, 
that of the comet of 1846. 
It is infinitely im- 
probable that these 
coincidences should 
be accidental : they 
point, undoubtedly 
to a common origi 
of the two bodies, 
The theory of com- 
ets now generally 
accepted is that they 
enter the solar sys- 
tem ab extra, move 
in parabolas or hy- 
perbolas around the 
sun, and, if undis- 
suf... F184 JOLIN 02... Lit cae 
planetary a arbe. 
tions; their orbits being sometimes transformed into ellipses. 
The new orbits of such bodies would pass very nearly through 
the points at which their greatest perturbation occ : and 
ca 
