( 4 " )

M. Römer’«

M<i’ ution ofLight dcfendej,

lb. s. 354 .

Vld. S**f.

. ' d

“h.

1

it ■ tu

’P criod. Secundi 3

>7

54 3 ß ve ' lT «"7 Pcv. Primi.

Period. Tertii 7

3

59

39 xx ßve t\.TT I{cv. Primi.

P erioJ. Quarti 16

18

5

6 50 ßve 9rr Rcv. Primi.

Whence the Table

of tlie

First

/Equation of the First Satellite, or TU.

C/tJpms larger Table, may by an easie Reductiun ferve thc other three ; the./Equation os the xd. being irrt» or twice the Minutes with half 1<> manySeconds as thcre are Minutes in the yEquation of the First, and the grcatestEquation thereof Jh 1 zy. jF.quation of the zd. is 4,4 times greatcr•than that of the F irst, and when greatest amounteth to i 1 * xy /f . And thc/Equation of the 4 tb. being 9 .} times that of the F irst, is had by sübstract-ing I, and 1 from to times the iEquation of thc First, whcncc the -greatest:ibccomcs 6' 1 1 o’ x’S 1 '. fö that Xu>n. I. and Sum. II. as hcre collected for theFirst, may indifterently ferve all the reih

4. As to the Second /Equation of the other Satellites, As. Cajstni has, byhis pr.tcepta Calculi ( as iä before mentioned ) fuppofed the jMinutes tlrereofto bc increafed in the fame Proportion, as instead ol 14^ 1 c", in the First,to be a 8 ' xj'' in the Second, 57 ' xx f/ in the Tbird, and no lefs than i * 114' 7" in the Fourth\ whereas if rhis Second Inequality did proceed Irom theÜLicceilive Propagation of Light, this rEquation ought to be the fäme in allof them, which As. Cajstni fäys, was wanting to be Ihewn, to peifect AsKonter' s Demonstration; wherefore he has rejccted it as ist foimdcd. Butthere is goed Laufe to believe, that his Motive thereto, is what he hasthought not proper to difcover. And the following Oblerrations do füffrei-entjy liipply rite Defect complained of in the making out of that Hypathesis.

An. 1676, Ocl. X. Ihn. 6h io / 37 ». App. but 5h 37* Ep. Time.Ad. Cajstni at Pari} obferved the Emcrfion of the yd. Satellite from Japiter'sShadow. And again Net». 14. following 6h xc f yy 7 . App. Time, but 6*5* yyF. Er], Time, he obferved ehe lilce Emerüon of the fame Satellite. Th^•obferved Interval of Time between thefe Emerßons, was 43^ c 1 * 6* 18 W »which is xx H roore than 6 Mean Revolutions of this Satellite, of which4/ xj" arifes from the Difference of the First Aüquatibn, and the greatcr■Continuance of the Laster Eclipfe ; fö that the other 4 Miuutes is all that isleft to answer for the Difterence of the xd ASquations; and Xum. II. in thatTime increasing from 48 to jx, gives 4/ 36" for the Difference of' the xd.yRquations of the First Satellite. So that here the xd .Cquation of tlie Tbirdis found rathet lefs than that of the First, but the Difference is so fmall, thatit may rathet be attributed to the Uncertainty of Observat ihn. Whereas ac-cording to M.Cajstni's Method of Calculating, instead of four Minutes itought tobe i8 / 38^. and the Interval of thefe two Emcrfiorrt 43»? cd* xi r .cxceeding the Time obferved by a wbole Quarter of an Hour; which thatCurious Observer could not be deceived in.

The