[ 34-3 ] 
Upon the whole, the neceffity of fending an obferver 
into the South feas fufficlently appears, whether it be 
propofed to determine the fun’s parallax by the dif- 
ference in tho total duration of the tranht, or by the 
obfervations of the internal contadts either at the in- 
grefs or egrefs. For if there fhould happen to be no 
land in the meridian oppohte to Tornea° and in about 
21° of S. latitude j yet if an obferver can be Rationed 
either in the iflands of Mendoza, or in the iflands of 
Amflerdam and Rotterdam, a difference in paralladtic 
time will be obtained as in the following Table. 
Places compared^ 
Diiierencc 
in total 
duration. 
Difference 
at ingrefs. 
Differcucc 
at egrefs. 
.Tornea® and Mendoza Ifles 
Tornea® and Amflerdam orRotterdam 
Tornea® & the opp. merid. in 2 1 S. lat. 
/ " 
23 00 
22 41 
23 56 
/ " 
11 24 
13 12 
13 03- 
II 
9 29 
10 ^3' 
If the flcy ffould prove favourable, the obfervations 
made at Tornea° and in any of the above places will 
enable us to determine the fun’s parallax with great 
precifion,and independent of the exadl knowledge of 
the longitude of either place. But as the iituation of 
Tornea° is perhaps very exadtly known, if it fhould 
be convenient to the louthern obferver to continue 
long enough upon his ff ation to determine the exadt 
longitude of it, to which the fituation of Jupiter at 
that time will greatly contribute, both methods might 
be pradlifed at the fame time, and they would mu- 
tually confirm and illuftrate each other. 
An opportunity of obferving another tranfit of 
Venus will not again offer itfelf till the year JH74. 
It behoves us therefore to profit as much as poffible 
by . 
