30 OF THE FIGURE AND MOTION

the various vicissitudes of the seasons, summer,winter, spring, and autumn.

And the proofs of this second motion may beeasily gathered from celestial appearances, innearly the same manner as the former.' For asthat luminary seems to move round the earth,from east to west, in the space of a day, whichis really owing to the diurnal revolution of theearth upon its axis, in a contrary direction, so,likewise, he seems to have an annual motion inthe heavens, and to rife and set contiually indifferent parts of them ; which is certainly oc-casioned by the daily motion of the earth in itsorbit, or path round the sun, which it completesin the space of a year.

That the earth is not the center of the celestialmotions, may also be easily strewn from the re-volutions and appearances of the different planetswhich belong to our system. For it is certain,that wherever the fun be placed, the orbit ofVenus surrounds and incloses him within itself;and therefore Venus, whilst she describes thisorbit, must really move round the fun. Forthis planet is observed to be sometimes above,or beyond the fun ; and sometimes below him,or between the fun and us: but she was neverknown to come in opposition to the fun, or tobe seen in the east when he was in the west ;which must necessarily have happened, if she

had