C ^39 ) 
A (econd Inequality is that which depends on the diftanca of the 
Sun from Jupiter^ which he hysMonfiQur Romer did moil mgQniouQy 
explain by the Hypothefis of the Motion of Light; to whlchyttCfifm 
by his manner of Calculus feems not to affent, though it hard to 
imagine how the Earth's Portion in refped of Jupiter fiiould any- 
way affed the Motion of the Satellites. This Inequality he makes to 
amount to two Degrees in t\\Q SateUitesMoiiovi^ov 14'. 10''. of Timc^ 
wherein he fiippofes the Eclipfes to happen fo much (boner when Jw 
/)/>^r Oppofes the Sun, than when he is in Conjundion with him 
The diftribution of this Inequality he makes wholly to depend on 
the Angle at the Sun between the- Earth and without any 
regard to the Excentricity of Jupiter ^ ( who is foractimes | a Semi- 
diameter of the Earth's Qrb farther from the Sun than at other 
times) which would occafion a much greater difference than the 
Inequality of Jupiter and the E^jr^Fi Motion , both of which are 
accounted for in thefe Tables with great Skill and Addrefi. But what 
is moft ftrange, he affirms that the lame Inequality of two Degrees 
in the Motion, is likewife found in the other Satellites^ requiring 
a much greater time, as above two Hours in the fourth Satellite : 
which if it appeared by Obfervation, would overthrow Monfieur Ra- > 
wer's Hypothefis entirely. Yet I doubt not herein to make it demon- 
ftratively plain , that the Hypochefis of the progreffive Motion of 
i Light is found in all the other Satellites of Jupiter to be neceifary^ and 
I that it is the fame in all; rhere being nothing near fo great an Annual 
I Inequality as Monfieur Cajjini fuppof^s in their Motions, by his TablepI 
pag. 9. and his Fr^cepta Calculi. The Method however ufed to com- 
\ pute this is very Curious; for having found that whilft the Sun re- 
; voives to Jupiter^ there pafs ;98^- 21^- 15'. wherein are made 225 | 
Revolutions of the Satellite to j^^^p/m-/ the Number of Revoluciojis 
I fines Jupiter was Lift in Oppofirion to the Sun^is what he calls I^am. 11.^'-' 
in which the Inequality of the Earth's xMotioa is allowed for in the 
Months, and that of Jupiter s Orb by a Table of the iEquarion of 
1 Num.li^ amounting in all co 5 I Revolutions of the Satellite zo Jupiter. 
; This in the Tables following I have thought (it to leave out, jhe^.vini;^ 
'j how to find it by help of the former iEquacion of A^/m. L The:;; 
I \ Numbers are in eiTedl the fame with Monfieur Cajflms, only reduced • 
t|to our Stile and Meridian, and the form of them abridg^d^ snd^xis ■ 
; ' hoped amended. See Philof. Tranfad. N*^- 136. 
O o 2 
