Mathematical tracts on the lunar and planetary theories, the figure of the earth, precession and nutation, the calculus of variations, and the undulatory theory of optics.

122 PLANETARY THEORY.
The perturbation in latitude may be calculated from the'
equation
d2z + m z
rn Z
('+ y '2 )i
which being integrated as in the note to (87), the tan. latitude or - is found.
r
The latitude may also be found by investigating the
variations of the longitude of the node and of the inclinations. For this, as well as for the peculiarities of the
theory of Jupiter's satellites, and other more recondite parts
of the Problem of Three Bodies, we refer to the Encyclopedia Metropolitana Art. Physical Astronomy, to Woodhouse's Physical Astronomy, to Lubbock's Essays, to the
Mécanique Céleste of Laplace, or to the Théorie Analytique of Pontécoulant.