( 4°9 )

Hiart. 19*1. 6h 45 - Alt. Jov. 19° 35s Satelles Primus ad Limbum Jovis 1&.4037:appropinquabat, cui 7^ 51^. jungebatur.

Ati. 1672. Ap. 15. 7 51 43'. velp. Ait. 25° oo'. Satelles Primus mox."- 9 *- ?■ 4 ° 99 ’Jovem a tergo subiturus j. circiter diametri a Limbo ejus, apparuit.

8 h 6'. Alt. y 27° 20/. subivit Jovem. Alt. Jove 27 0 26s ccrsr non con-spiciebatur.

4. Jul. 6. (st.n.) 167 5. ante mediam noctem, hora seil. 11. & 1 6. Se- \ b

eundis praecise, Secundus Jovis Satelles Egredi incipiebat ex Planetae hujus, Ht \ l7m ,, ^,,7qui ipliim obscuraverat, umbra.

5. An. 1679. Jun. 7. st. n. zsc m. I discovered 3 Satellites of Jupiter : ph ' Cal ‘ ”• '•The First was distant Westward of the Limb of Jupiter , a little leis than aDiameter; the Second was distant, onthe East-side, a little more than a Dia- §• LXIV. 2.meter. The Third was more Eastward than the Sccond , by soniewhat leis

than a Diameter of Jupiter.

XCI. 1. Let A be the Sun, B Jupiter , C the Firß Satellite of Jupiter, Tbe £<i u *<!on 0/which enters into the Sbadow of Jupiter, to come out of it at D; and let Romer^.rjs.EFGHLK. be the Eartb placed at divers Distances from Jupiter. p. 893 .

Now supposc the Eartb, being in L towards the 2 d Quadrature of Jupiter, F, £' I45 'hath scen the First Satellite at the Time of its Emeision, or Istuing outof theShadow, in D ; and that about 42s hours aster ( vid. aster one Revolutionof this Satellite ) the Eartb being in K, doth sce it returned in D ; it is mani-fest, that if the Light require time to traverlc the Interval LK, the Satellitewill be scen returned later in D, than it would have been if the Eartb hadremained in L, so that the Revolution of this Satellite being thus obscrvedby the Emerstons will be retarded by so much time, as the Light (hall havetaken in palnng from L to K, and that on the contrary, in the other Qua-drature FG, where the Eartb by approaching goes to meet the Light, theRevolutions of the Immcstons will appear to be shortned by so much, as tholeof the Emeisions had appeared to be lengthened.

This ncw Equation of the Motion of Light, which hath been establishedby the Royal Academy, and in the Obfervatory for the Space of 8 Years, wasconfirmed by the Emerfion of the First Satellite obscrv’dat Paris i6j6. Nov. 9.

5 h 2 s' 4 > // , atNight, r o' later than it was expected, bydeducing it from The Theoryofthole that had been Obscrved in the Month of Autust, when the Eartb was J u P lte '"sSatct-much nearer tö Jupiter. CaUinis». .28.

f. 68 i.

XCI 1 . i. M. Castini , having formed a ncw Hypothefis for the Satellites of M c ss ;i/Jupiter, disterent from that of Galileo, thinks that the Plain of their Orbs is TMe s ,for tbeE-Inclined to the Plain of the Eclipticis, He scttles their Nodes with the Orbs °f >heof Jupiter towards the 13 0 of Leo and Aquarius ; and finds that the Obliqui- of Jupiterfi-f-ty of their Circles to the Orbite of Jupiter, is almost double to the Obliquity of hnsted, and Re-this Orbite to the Ecliptique. ttendLVlf

2. M. Castini, in the last Treatisc of a Book, Entitul’d Pccucil d 1 Obster- London \ hyvations faites en Plufi&urs Voyaies, iste, has employed his Skill, to make easie Edra *

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