428 Dr. Maskelyne’s Advert ifement of 
The comet in queftion is alfo, from the pofition of its orbit* 
liable to be much difturbed both by Jupiter and Saturn, par- 
ticularly in its afcent from the fun after pa fling its perihelium* 
if they fhould happen to be near it, when it appoaches to or 
erodes their orbits ; becaufe it is very near the plane of them at 
that time. When it palled the orbit of Jupiter in the be- 
ginning of February 1682, O. S. it was 50° in confequentia of 
that planet; and when it palled the orbit of Saturn in the- 
beginning of Odlober 1663, it was 17 0 in confequentia of it* 
Hence its motion would be accelerated while it was approach- 
ing towards the orbit of either planet by its feparate action,, 
and retarded when it had paffed its orbit; but, as it would be 
fubjedted to the effc£b of retardation through a greater part of 
its orbit than to that of acceleration, the former would exceed 
the latter, and confequeiitly the periodic time would be 
fhortened ; but probably not much, on account of the confl- 
derable di dance of the comet from the planets when it palled 
by them ; and therefore we may ftill expedb it to return to its 
perihelium in the beginning of the year 1789, or the latter 
end of the year 1788, and certainly fome time before the 27th 
of April 1789. But of this we fhall be better informed after 
the end of this year, from the anfwers to the prize queftion 
propofed by the Royal Academy of Sciences at Paris, to com- 
pute the difturbances of the comet of 1532 and 16.61, and 
thence to predidl its return *. 
* Since this was written, I received the unwelcome news*, in a letter from 
M. Mechain, of the Royal Academy of Sciences at Paris, that the Academy 
bas not received fatisfadtory anfwers concerning the difturbances of the comet 
between 1532 and 1661, and 1661 and the approaching return, and that the 
prize is referred to be adjudged of at Eafter 1788, and that it will be 600a 
livres. N„. M. 
7 
If 
