Royal Society. ii 
ing, from the time of the former, ^6,0 h. 23 m. if it be the 
third year after biflextile^ otherwife fubftraft 2d. oh. 23m. 
only: Having found thefe, it will be an eafy matter to continue 
the calculus for all the conjunctions of Mercury with the fun, and 
that with the greatclt certainty ; by addition only, the moments of 
conjunctions and the diftances of the planet from the centre of 
the Itin are obtained j whence likewile by the help of the table, 
the durations of thefe ecliples, are difcovered, lb that nothing 
feems to be wanting in this affair: As to the EpochdP-, thefe are 
with more fafety had from the induftry of obfervers than by the 
fubtileft calculations - therefore Mr. Halley chofe for the firil 
cafe, that remarkable tranlit of Mercury which he himlelf had 
fully obferved at St. Helena^ OBober 28, 1(^77 O. S. and whole 
middle he determined there at o h. 4 m. p. m, but at London o h. 
^%X£i.p.m. The way in which the planet leemed to advance 
was 4' 40'' more northerly than the lian*s centre : In the other 
cafe, viz. when Mercury was in conjunction with the fun 
April 23, \66x O. S. he appeared at his lead diflance from the 
fun's centre at 2)antzic <5 h. 8 m. p, m. and at London 4h. 52 m. 
being then in the middle of his tranfit, and at the fame time was 
diftant from the fame centre 4' 27'/ to the north 5 hence accord- 
ing to the above rules, it was an eafy matter to exhibit in order 
all the vilible conjunctions o^ Mercury with the fun. 
A feries^ of the times wherein Mercury ^ being in conjunfiion 
with the fun, is feen within his dillc, calculated for the prefent 
and enfuing century, with the diftances of the planet from the 
fun's centre. 
In the month of A p r i l 
Years 
'i'lmes 
ot LonjunCt. 
Diit.tromthe 5un's C^entrel 
d. 
h. m. 
' // 
i5i5 
22 
21 38* 
7 20 
N. 
161^ 
25 
5 15* 
9 35 
S. 
1661 
-3 
4 52 * 
4 27 
N. 
1^74 
16 
12 29 
12 28 
S. 
1707 
24 
12 6 
I 34 
N. 
1720 
26 
19 43 * 
15 21 
S. 
1740 
21 
II 43 
15 35 
N. 
1753 
24 
19 20 * 
I 19 
S. 
i']%6 
22 
18 57* 
12 43 
N. 
^199 
16 
2 34* 
4 12 
S. 
B 
In 
