Sect, i. Of the SOLAR SYSTEM* ij

the apparent Revolution of the Heavens*and of all the Stars round it, in the Spaceof a natural Day. The Solar Spots do notalways remain the fame, but sometimes oldones vanish, and afterwards others succeedin their room; sometimes several small onesgather together, and make one large Spot,and sometimes a large Spot is seen to bedivided into many small ones. But, not-withstanding these Changes, they all turnround with the Sun in the same Time.

The relative Distances of the Planets from the

the Sun, and likewise from each other, ar Usancesdetermined by the following Methods: First, 0 / the pi«.the Distances of the two inferior Planets J Th? sin areand J from the Sun, in respect ofthe Earth’s d n e e ^ mi 'Distance from him, is had, by observingtheir greatest Elongation from the Sun asthey are seen from the Earth.

The greatest 'Elongation of Venus is founds- 5.,by Observation to be about 48 Degrees,which is the Angle ST § ; whence, by theknown Rules of Trigonometry, the Propor-tion of S 5 , the mean Distance of Venusfrom the Sun, to ST, the mean Distance ofthe Earth from him, may be easily found:

After the same Manner, in the right-angledTriangle S T 5 , may be found the DistanceS 5 of Mercury from the Sun. And ifthe mean Distance of the Earth from theSun ST be made 1000, the mean Distanceof Venus S 5 from the Sun will be 723 ;

and