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Mr. Hind and Prof. Weiss. It was found to present a very great resemblance 
to tbe orbit of the Great Comet of 1843 : a resemblance so close, that it seems 
almost certain that they must belong to the same body, that is, the comets 
of 1843 and 1880 must be different apparitions of the same body. This 
would give it a period of 37 years. 
The great comet of 1843 was one of the most magnificent comets which 
have appeared. It suddenly made its appearance on February 28, having 
passed its perihelion passage on the previous day, and was so brilliant that it 
was distinctly visible at midday, quite close to the Sun, and could even be 
seen in broad daylight with the naked eye. It passed so close to the Sun, 
that in one day it swept over three-fourths of its entire orbit, and moved off 
into space with enormous velocity, carrying a great and brilliant tail as it 
went. This comet excited much attention at the time, and numerous attempts 
were made to calculate its orbit, and determine whether it had been pre- 
viously seen. The resulting orbit was uncertain, especially as to the period 
of the comet, the observations being too close together to enable its true 
period to be made out. Any period from 7 to 700 years seemed possible. 
It was suspected that this comet of 1843 might be identical with a very 
similar comet which suddenly made its appearance in March 1668, and was 
remarkable for its great and brilliant tail : its orbit seems to be almost iden- 
tical with that of 1843. Another comet which it was also thought might be 
identical with that of 1843, was the comet seen in 1689 ; the orbits closely 
resembling each other. So do the orbits of brilliant comets which became 
suddenly visible in 1695 and 1702. The very bright comet of 1618 also seems 
to have had a similar orbit, and to have been of very analogous character. 
For this reason it was suggested that perhaps all these comets were appa- 
ritions of the same body, with a period of seven years, though it seemed 
extraordinary that it should not have been visible between 1702 and 1843. 
If the period be taken at thirty-seven years, as indicated by the interval 
between 1843 and 1880, it is obvious that its prior appearances must have 
been in 1732, 1695, 1658, and 1621, which would exclude all these comets but 
that of 1695, which both Mr. Hind and Prof. Weiss think was probably an 
apparition of this comet. It is also thought that it might possibly be the 
same comet as that seen in 1618. From the position occupied by this comet 
it is one which may easily be overlooked at any of its reappearances, and, 
as pointed out by Mr. Marth, may have a period of only eighteen and a half 
years, as it would pass its perihelion in the intermediate returns in July, and 
very easily escape detection. 
As there is a possibility of the comet having as short a period as seven 
years, it is probable that astronomers will be on the look-out for it at the 
epoch of its next possible appearance (January 1887) with the view of 
detecting it. If properly looked for it might possibly be seen before its 
perihelion passage. 
BOTANY. 
Sensitiveness vn the Acacia. — Mr. T. L. Phipson has communicated to the 
French Academy of Sciences ( Compt, Rend ., 24th May, 1880), some curious 
