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fure before thefc Obfervations. There remained to find by Ex- 
pericnGCjwhether Jupiter did turn about his Aocis^ as many believe, 
that the £ar/i turns about ber's. And d\\.\\oug\\mo^ A Jironomers 
had conjedlur djit did fo^either by this Analogy,or by other Con- 
gruities , yei it was much wifti'd^that we might be afTured thereof 
by Obfervations* And this it is, for which weare obliged to 
M. CaJJmi, who, having by the advantage of the fame Glaiies dif- 
covef d feveral changes , as well in the three obfcure Behs^ com- 
monly feen in Jupiter^zs in the reft of his Dts^e.^nd having alfo ob- 
ferved Spots in the midft of that Planet^ and fometimes Bri^htneJJes, 
fuch as have bin formerly feen in the tSz/^/jhath at length difcover'd 
a Permam?it Spot'm the Nd?ri^/;mi part of themoft S outhern'^t\t''^hy 
the means whereof^he hath concluded^that Jupiter turns about his 
Axij in 9. dayes,y6. rainutes,and makes 29. whole circumvolutions 
in 12. dayes 4. minutes of ours, and 3(^0. in i4g. dayes. For he has 
found5that this Spot was not cauf:d by the Shadow^ any Satellite 
as wellby reafonof itsSituntion, as becaufe it appeared, when 
there could be no Shado w. Befides,that its motion differed from 
that of the Shadows, which is almoft equal, as well towards the 
Edges as towards the Middle of Jupiter : Whereas, on the contra- 
ry, this haih all the accidents, that muft happen to a thing, 
whicli is upon the furf^ce of a round Body moving 5 for example, 
to move much rnore flowly towards the Edges , than towards the 
Middle, and to pafs over that part, which is in the middle of the 
Diske, equal to the half of che Diameter in the fixth part of the 
time^it takes to make the whole revolutionJie having feen this half 
pafs'd over^in 99 or rco minutes juft,as it mnfi happen, fuppofing 
the whole circumrotation is made in 9. hours ^6, minutes. 
He hath n^tyet been able to determine the Situation of tlie 
Axts^wpou wh ch this motion is made^bocaufe the ^f//^/, according 
to which it is raade,have for fome years appeared ftreighrthough 
m the precedent years , other Ajirommsrs have feen them a L'tcle 
crooked : Which flieweth, that ih^ Axis of the diurnal motion of 
Jupiter \s a little inclined to the plain of the EcUptick. But in time 
we may difcover^ what certainty there is in this matter. 
After' this excellent Difcovcry, he hath calculated many T^^/^/, 
whereof he gives the Evplication and Life in the Letters by him 
r T \.\ *^ * * addrelTed to the Abbot Falcoiiieri, By the 
Thefe Tables are mt yet ^ . , 7 t • 
fentcverM'i'tisho cd, means of them 5 one may know, i^hent\m 
wllbi, ne long. Spot yntiy be feen by us: For.having firft con- 
fidered 
