640 PHILOSOPHICAL TRANSACTIONS. [aNNO 1683. 



45' 20''; their difference of longitude is 48° 43' 56", and Jupiter's place in Leo, 

 19° 34' 3g". 



Hence Jupiter's place in consequence of Saturn's 1 3' 20", with which, and the 

 distance of their centres, observed the same night, 20' 12', I lind the true differ- 

 ence of their latitudes J 5' 20''; only half a minute different from what I assumed 

 it on the authority of the tables. 



The apparent motion of Jupiter from the 14th to the 18th day of October, by 

 an ephemeris exactly calculated, and made agreeable to these observations, is 

 29' 16', of Saturn 15' 01^', both direct; hence the motion of Jupiter from Saturn 

 in 4 days, is 14' 15^'. I say therefore, as 4 days motion, or 14' 15'', is to 4 

 days or 96 hours, so is 13' 20", which Jupiter is past the conjunction of Saturn, 

 to 90 hours, or 3 days 18 hours, the time interlapsed since the conjunction; 

 which taken from the 17 th day 15 hours, the time of my observation, gives the 

 true time of the conjunction of the two planets on the 13th day 21 hours after 

 noon, or according to the common account, the 14th day at 9 o'clock in the 

 morning. At which time Saturn is with Jupiter in 19° O' 7-r of Leo, with 15^ 

 more northern latitude. 



The Acta Eruditorum Lipsiensia, page 366, make this conjunction to have 

 happened the same day in the same longitude with the 11th star of Leo; whose 

 place they state in Leo 19° 4', latitude 0° 16' north, with 14' difference of lati- 

 tudes between the two planets. But their observation seems to have been made 

 only by the judgment of the bare eye, without an instrument, which consider- 

 ed, I wonder not that it differs at all, but rather that the difference is so small 

 from this determination. 



An. l683, Jan. 19, viewing the planets, then both retrograde, with the 16- 

 foot glass, I found them approached within a measurable distance of each other; 

 when I began to take the following measures : 

 l683 h. m. 



Jan. 19, 6 41 .. between their centres ° 33' 28^ 



45 . . repeated 33 24 



49 . . between the remote limbs 33 52 



Jan. 26, both planets being in ^ to the sun. 



26, 6 3 . . between their centres 15 8 



7 . . repeated j 5 6 



7 . . between their remote limbs 15 31 



12 . . between their centres 15 5 



14 . . repeated 15 2 



17 .. between their next limbs 14 29 



20 ..repeated , 14 21 



