374 Proceedings of Royal Society of Edinburgh. [sess. 
appears to be the orbit of the Comet 1556, perturbed by a planet 
considerably larger than Jupiter,* situated at or about the position 
indicated as to radius vector and longitude in my original com- 
munication to the Royal Society of Edinburgh in 1880, according 
to which the planet is at 100 times the mean distance of the 
earth from the sun, and is in longitude 181° in this year 1901. 
With regard to Comet 1843 ii., if this be a reappearance of 
Comet 1556, the Nodes have been retrograded, the inclination 
increased, and the longitude of perihelion advanced, as in the 
other case. But the latitude of aphelion has not been reduced 
like the other, but rather increased. Also the Perihelion distance 
has been increased quite sufficiently to account for the inferior 
display and the insignificance of its last appearance. 
It would be rash to make any further expression of opinion 
until the calculations have been completed. In the meantime the 
conclusions certainly arrived at are the following : — 
1. The position of the new planet as stated in 1880 is con- 
firmed by a fuller investigation on the same lines. 
2. If the comets of 1264 and 1556 were identical, the new 
planet would produce perturbations whose amount is 
sensible, and these account for the non-reappearance of the 
comet in its old orbit, and may lead to further knowledge 
about the mass and position of the new planet. 
3. It is possible that one of the comets, 1844 iii. or 1843 ii., 
may be the lost comet of 1556, perturbed in its orbit by 
the new planet; and the re-examination of the 1556 
observations, and the computations which I am now 
engaged on, must throw some light on this question. 
* In the paper which I read to the R.S.E. in January, 1881, the perturba- 
tions of Uranus by the new planet led me to estimate its mass at a little more 
than half that of Jupiter. 
