BOOK II.

~CHAP. 1.~ _That the planets move in a space empty of sensible matter_ p. 161 _The system of the world described_ p. 162 _The planets suffer no sensible resistance in their motion_ p. 166 _They are not kept in motion by a fluid_ p. 168 _That all space is not full of matter without vacancies_ p. 169

~CHAP. 2.~ _Concerning the cause that keeps in motion the primary planets_ p. 171 _They are influenced by a centripetal power directed to the sun_ p. 171 _The strength of this power is reciprocally in the duplicate proportion of the distance_ ibid. _The cause of the irregularities in the motions of the planets_ p. 175 _A correction of their motions_ p. 178 _That the frame of the world is not eternal_ p. 180

~CHAP. 3.~ _Of the motion of the moon and the other secondary planets_ _That they are influenced by a centripetal force directed toward their primary, as the primary are influenced by the sun_ p. 182 _That the power usually called gravity extends to the moon_ p. 189 _That the sun acts on the secondary planets_ p. 190 _The variation of the moon_ p. 193 _That the circuit of the moons orbit is increased by the sun in the quarters, and diminished in the conjunction and opposition_ p. 198 _The distance of the moon from the earth in the quarters and in the conjunction and opposition is altered by the sun_ p. 200 _These irregularities in the moon’s motion varied by the change of distance between the earth and sun_ p. 201 _The period of the moon round the earth and her distance varied by the same means_ ibid. _The motion of the nodes and the inclination of the moons orbit_ p. 202 _The motion of the apogeon and change of the eccentricity_ p. 218 _The inequalities of the other secondary planets deducible from these of the moon_ p. 229

~CHAP. 4.~ _Of comets_

_They are not meteors, nor placed totally without the planetary system_ p. 230 _The sun acts on them in the same manner as on the planets_ p. 231 _Their orbits are near to parabola’s_ p. 233 _The comet that appeared at the end of the year 1680, probably performs its period in 575 years, and another comet in 75 years_ p. 234 _Why the comets move in planes more different from one another than the planets_ p. 235 _The tails of comets_ p. 238 _The use of them_ p. 243 244 _The possible use of the comet it self_ p. 245 246

~CHAP. 5.~ _Of the bodies of the sun and planets_

_That each of the heavenly bodies is endued with an attractive power, and that the force of the same body on others is proportional to the quantity of matter in the body attracted_ p. 247 _This proved in the earth_ p. 248 _In the sun_ p. 250 _In the rest of the planets_ p. 251 _That the attractive power is of the same nature in the sun and in all the planets, and therefore is the same with gravity_ p. 252 _That the attractive power in each of these bodies is proportional to the quantity of matter in the body attracting_ ibid. _That each particle of which the sun and planets are composed is endued with an attracting power, the strength of which is reciprocally in the duplicate proportion of the distance_ p. 257

_The power of gravity universally belongs to all matter_ p. 259

_The different weight of the same body upon the surface of the sun, the earth, Jupiter and Saturn; the respective densities of these bodies, and the proportion between their diameters_ p. 261

~CHAP. 6.~ _Of the fluid parts of the planets_

_The manner in which fluids press_ p. 264 _The motion of waves on the surface of water_ p. 269 _The motion of sound through the air_ p. 270 _The velocity of sound_ p. 282 _Concerning the tides_ p. 283 _The figure of the earth_ p. 296 _The effect of this figure upon the power of gravity_ p. 300 _The effect it has upon pendulums_ p. 302 _Bodies descend perpendicularly to the surface of the earth_ p. 304 _The axis of the earth changes its direction twice a year, and twice a month_ p. 313 _The figure of the secondary planets_ ibid.