70 
POPULAR SCIENCE REVIEW. 
expressed the opinion that the two were probably identical. Later in- 
vestigations confirmed this view, and showed that the comet strongly 
resembled in its orbit the comet visible in the years 1444 and 1569. It 
would therefore appear to have a period of some sixty-two years. Dr. 
Schur and Herr Hartwig, from their investigations, assign to the comet a 
period of 62£ years, and the following elements : 
Perihelion passage, 1880, September 6 
Longitude of perihelion 
Longitude of ascending node 
Inclination of orbit 
Eccentricity of orbit . 
Semi-axis major .... 
5894, Berlin mean time. 
. 83° 33' 28" 
. 44 33 30 
.38 8 56 
. 0-97764 
. 1-5756 
The o^bit of the comet extends, therefore, beyond the orbit of the 
planet Neptune ; but owing to the great inclination of the orbit, it cannot 
be much affected by the perturbation of any of the greater planets. The 
comet, however, approaches very close to the orbit of the planet Mercury 
at the ascending node; and Prof. Winnecke is of opinion that it may be 
due to the attraction of this planet that the comet has been introduced into 
the solar system with its present elliptical orbit. For though at present 
the orbits do not approach each other sufficiently near to enable the planet 
to very importantly affect the motion of the comet, at some past period 
the two orbits may have been nearly coincident, though now separated by 
the effect of perturbation. 
Swift's Comet . — On Monday, October 11, 1880, Prof. Lewis Swift, of 
Rochester, New York, discovered a large comet in the constellation Pegasus, 
but no observation seems to have been obtained during the month in 
Europe. On November 7, 1880, a bright comet was discovered at 
Dun Echt Observatory, belonging to Lord Lindsay. A day or two showed 
that the two comets were identical, and revealed in the constellation Lacerta 
that the orbit of the new comet coincided very closely with that of 
Comet 1869. This comet was discovered by Herr Temple, on November 27, 
1869, in the constellation Pegasus a few days after its perihelion passage, 
and it was last seen at Leipzig on December 31st. On November 29, 1869, 
it was described by Dr. Vogel as a very faint object of considerable dimen- 
sions, being nearly 6' in diameter. From observations spread over a 
month, Dr. Bruhns calculated a parabolic orbit, whose elements he found 
to be — 
Perihelion passage, 1869, November 20-854, Berlin mean time. 
Longitude of perihelion . . . .41° 17' 13" 
Longitude of ascending node . . . 292 40 29 
Inclination of orbit . . . . . 6 55 0 
Perihelion distance 1*1026 
Dr. Bruhns remarked, however, that this orbit did not closely represent 
the observations, and seems almost to have suspected the elliptical character 
of the orbit. The close resemblance between this orbit and that calculated 
from the observations made of the comet of 1880 is shown by the elements 
for the latter comet calculated by MM. Zelbr and Hepperger : — 
