subject, therefore, to the third law of Kepler. The compression of

their primary and their reciprocal attraction retains their orbits in the plane of the planet's equator.

introduced by integration into series of perturbations 299, 312

sum of, zero on two of the co-ordinate planes and a maximum on

79

203

182

145

406

407

138

140

399

178

178

motion of the same, as if the masses of the planets were

Coefficients of the series expressing the disturbing action of the planets

239

INDEX.

Ellipticity of sun, effects of on the motions of the planets

343

of gravity, varies inversely as the square of the distance

168

intensity of on earth, determined by the length of the seconds

pendulum

48

47

101

varies as the square of the sine of the latitude

Gyration, centre and radius of