JUPITER. 



7S" 4 for 4 lialf periods ; lience, the greateft equation 20' 

 49 '5 : 6' 40". 2 :: 73".4 : 26', which (as the time is before 

 1750) added to 6' 40". 2, gives 7' 6". 2, the equation for 

 May 16, 13^;. This, however, is only an approximation. 

 We calculate for half periods, becaufe then all the argu- 

 ments return again the fanse. Now from that time to the 

 given time, that is, July 11, y", the interval is 0.J3 of a 

 year ; and for 10 years, the increafe of the equation :s I ".7 ; 

 hence, 10 : 053 ;: i"." : o".og, the variation in 0.53 of a 

 year; which added to 20' 46', gives 20' 46".09, or 20' 

 46". 1 , taking it to the aearell tenth of a fecond, the great 

 equation. The arguments of the great equation are taken 

 from the year 1780, they not having fenlibly altered from 

 that time to the given time. The fums of all the columns 

 give the longitude corretted by the great equation, the 

 aphelion, the node, and the arguments, for the given time. 

 The Arguments I, X, XI, are immediately found accord- 

 ing to the rule. The equation to Argument I. is thus 

 found : the Argument is 20" 7' 58". Now in Table VII. 

 the equation anfwering to 20' is — l' 46' 59 ', and the va- 

 riation for 60' is 5' 9'; hence, 60' : "' 58'' :: 5' 9" : 41", 

 which (as the equation is increaling) added to — i- 46' 59", 

 gives — I 7' 40', the equation required. And to find die 

 fecular variation, that variation is — l6".98 for 20 \ and it 

 changes o".82 for 60' ; hence, 60' : 7' 58" :: o".82 : o" 1 1, 

 which (as the variation increafes) added to — 16". 98, gives 



17'' 09, the fecular variation correfponding to the given 



argument. Now this fecular variation is reckoned from 

 1750, and from thence to .July ii, 17S0, there has elapied 

 30.53 years; hence, lOO : 30.53 :: — \~"o<) : — 5" 2, tlie 

 fecular variation for 30.53 years. With 90S0 take the 

 equation from Table VIIl. Now the equation is i' 30^.6 

 for the Argument 9000, and it changes 3".7 for ico; 

 hence, 100 : 80 :: 3".7 : 3", which (as the equation is in- 

 creating) added to i 30".6, gives i' 33".6, the equation re- 

 quired. By proceeding thus to Argument XI. we get all 

 thefe equations. And by taking the difference of the pofi- 

 tive and negative parts, we obtain i"4S' 57 '.8, the value of 

 thefe 1 1 equatiom^ which applied, with the proper fign, to 

 7' °^ 57 53"-9> g'^*^^ ^^ -9 '^ 5*5 '.I, the longitude of Ju- 

 piter in his orbit. Now for the reduftion of this to the 

 ecliptic, we have Argument XII. = 3' 20' 56' 24"; and 

 the reduftion in Table XXIV. is 4- 17".5 for 3^ 20 ; and 

 n changes o'' 7 for Go'; hence, 60' : 56' 24" ;: o".7 : o''.7, 

 taking it to the neareft tenth of a fecond ; and this (as the 

 reduftion increafes) added to + 17 '.5. gives ^- 3S".2, the 

 reduftion, which applied to 6' 29 8' 56".!, gives 6' 29 9' 

 I4' 3, the true heliocentric longitude of Jupiter in his orbit, 

 from the mean equinox. With Argument XII. enter 

 .Table XXIII. and the latitude for 3= 20'' is i" 46' 16" N., 

 and the variation is 29'' for 60'; hence, Oo' : 56' 24" :: 

 29" : 27", which (as the equation is dirainifliing) fubtraded 

 from i"46' 16' N., gives l^ 13' 49" N., the latitude un- 

 correfted for the fecular variation. Now for 3= 20 56' 24", 

 the fecular variation is — 20".), as we n ay take it the lame 

 as for 3' 21'; and the time from 1750 being 30.53 years, 

 6", the iecular varia- 



ve hav 



100 : 30.53 



20".5 : 



tion for 30.53 years, and thus applied to 1-=; 13' 49 



13 43" 



N., the true heliocentric latiti 



jf Ju- 



gives 

 piter. 



G'men the heliocentric latitude and longitude of Jupiter ; to 

 find the geocentric latitude and longitude, and his di/lar.ce from 

 /he fun and earth. 



Example.— 7'5 fnd the geocentric latitude and longitude of 



Jupiter, and his dijla 

 al 5' 49' mean time. 



Hel. long. Jupiter 

 Longitude earth 



•from the earth, or. July II, 



6 29 9 14..^ 



9 19 52 28.3 



Jupiter, among Alchemifls, fignifics the philofophers' 

 gold. The gentlemen of this profeffion apply every thing 

 to their art, which the mythologifts mention of the god 

 Jupiter, pretending that the ar.cient fables are to be undcrllood 

 in a figurative fcnfe : for infiance, Jupiter is the mailer of 

 the gods ; and gold, fay they, is the moft precious of 

 metals. Mercury is the ambaffador of Jupiter ; and this 

 fhews with how much eafe Mercury infinuates into every 

 thing. Jupiter holds the thunderbolt as his fceptre ; which 

 evidently points out the external fulphur uftd in projection. 

 Juyiter has the heavens for his ordinary habitation ; this 



fhew» 



