124 Astronomy.

Saturn has jive Moons', and besides

tl^

a stupendous Ring surrounding his

K

Half of its Orbit C F D, its apparent Motiondirect, or from Weft to East along the Line C V J y.while it describes the other Half DEC, its apP^iMotion is retrograde, or from East to West backalong the Line from D to C. So that eachtraverses the Diameter of its Orbit twice in eachvolution.

5 - The Moons of Jupiter severally shew tb e pPhases to him as ours does to us. They difrly iS

fiom

our

Sight

sometimes, so that

every time they come to the Shadow of JupitcJ ^ t 0F. Also, supposing the Earth at T, the Sates ,tewill undergo an Qccultation behind the Body

F. Also, supposing the Earth at T, the Satetlk e y^<<ter , as is evident from the Scheme. Again, a e (t'

as is evident from the Scheme,wili sometimes lose its Lustre as it pastes overlighten’d Disk of its Primary ; as when it is at ^and the Earth in R and T. Lastly, One Sat s ppdO may disappear behind another at K, or causeSo disappear behind it at M. c tf'

7. The Observations by Telescopes have be e grried so far as to make it very probable that alltellites do really revolve about their own Axis, by

cf Spots which they have discovered to belong i>'and which by their Motion cause a greattbe Brightness of the Satellites, and sometime 3 qM'most obscure them : For which see Mr. Pound 3 ^.ppversions in Jones's Abridgconent of the Philosophic#'nflions, Vol. IV. p. 307. pfO'

8. By means of Jupiter’s Satellites several vobF^fl?Mems in Natural Philosophy have an easy and *

They - e

_ a, niat. ’tis very ie t°

have all the four in View at once ; nor is it pel 1 pknow which Satellite in Order you fee, butKnowledge of the Theory and Calculation, y'>the remotest Satellite may appear nearest to 7 .^ si'and the contrary, as is evident from a View of d 1gure. j

6. These Moons, like our own, softer an *