Dr. Bowditch, President of the American Academy. Xxxv 
the entire work, is, the Motions of the heavenly bodies about their 
own centres of gravity; under which head the author considers, 
in detail, the motions of the Earth, the Moon, and Saturn’s Rings, 
about their respective centres. 
In the Second Part of the work (which begins with the third 
volume, containing the sixth and seventh books), the author discus- 
ses the theory of the Planetary Motions, and their inequalities and 
perturbations, arising from all the known causes; beginning with 
the planet Mercury, and proceeding, in order, to the outer boundary 
of our system; excepting, however, the four newly discovered 
planets, Ceres, Pallas, Vesta, and Juno; the inequalities of which, 
as Dr. Bowditch observes, will not probably be completely ascer- 
tained for a long time.* In connexion with this part of his subject, 
La Place also considers the masses of the planets and of the moon ; 
the determination of which, as he observes, is one of the most 
important objects in their theory.t This portion of the work 
concludes with important considerations on the formation of astro- 
nomical tables, and on the invariable plane of the planetary system 
and the action of the fixed stars upon the system ; the great dis- 
tance of which last, as the author observes, renders that action 
insensible. f 
After the theories of the planets themselves, the author gives that 
of their respective Satellites ; beginning with the Moon, which occu- 
pies a large space (about half of the third volume), and which, as 
he remarks, has difficulties peculiar to itself, arising from the mag- 
nitude of its numerous inequalities, and from the slow convergency 
of the series by which they are determined. These inequalities, 
which arise partly from the oblateness of the Earth and Moon, and 
* Bowditch’s La Place, Vol. III. p. 187, note. 
+ Ibid, p. 333, t Ibid, p. 343. 
