[ 479 ] 
Places. 
Obferved dura- 
tions. 
L.diflance ofl 
centers from 
the durati- 
ons. 
L>. diftance 
deducedfrom 
calculation. 
Sun’s pa- 
rallax. 
h 
/ // 
/ // 
/ // 
// 
Tobol fki - - - - - 
<s\ 
OC 
Ln 
IaJ 
N> 
Lri 
9 5U53 
9 5 2 , 2 4 
10, 125 
Stockholm - - - 
5 50 43> 5 
9 54,85 
9 55, 8 3 
10,03 
Upfal ------ 
5 50 26 
9 55, 62 
9 55,95 
10,23 
Cajaneburg - - - - 
5 49 54 
9 55 , 61 
9 55, 61 
10, 00 
Tornea 0 - - - - - 
5 50 09 
9 55, 28 
9 5b, 08 
0 
0 
0 
— < 
By taking a mean of thefe determinations, we find 
the Sun’s parallax to be io",i. In the above calcu- 
lations the Sun’s femi-diameter was fuppofed = 
i5 / .48 // ,5, and that of Venus 29''. Obfervers, 
fays Mr. Pingre, have found the former to be about 
2" lefs, and the latter on the contrary half a fecond 
larger. By calculating upon the l'uppofition of a 
difference of 2" in the difference of the femidiameters 
of the Sun and Venus, the lead: diftance of the cen- 
ters at Tobolfki, Stockholm, Upfal, Tornea 0 , and Caja- 
neburg, ought to be 3", 12 lefs, and at Rodrigues 
2", 56 or 2 // ,6 o , and the Sun’s horizontal parallax 
ought alfo to be o'\iy lefs. If then this correction 
be admitted, which is warranted by the beft obfer- 
vations, the Sun’s horizontal parallax will be 
9 // ,92. 
There is ffill another method by which we are 
enabled to determine the Sun’s parallax, by compar- 
ing the obfervations made in different places where 
the effedt of parallax upon the planet is confiderable 
at the times of the two contadts. It was more con- 
venient to make ufe of the 2d internal contadt for 
this purpofe, and the obfervers were very advantage- 
oufiy ftationed at St. Helena and the Cape of Good 
q 2 Hope : 
