Bi ^'XRSTEONOMICATL- dnb 
tance of centers, ‘at the time ‘of tHe Vitible ecliptic conjunction ; 
Zo and Mo the diftance óf centers, at the time of the ex- 
ternal Contacts, = the fum of the femi-diameter of the fun and 
of Mercury == 9775 33 C 4 the vifible difference of latitude 
of the-centers, at the time of the firft external contact ; LM 
tlie vifible difference, at the time of the fecond ; Co — yF the 
vifible difference of longitude. of the. centers, at the time of the 
ud and oL at the time of the fecond external contact, 
For M# U, the angle of Mercury’ s vifible way. 
s Eii 32: UM 71", 566 :: Radius : Tangent angle 
roe 8* 18^ 15". 
| For 3M, the vifible tranfit line. 
-- Sine My U S7 I0 307 UM "ITIBO S Radius : yM 
495',512. Ast o and Mo are equal, the perpendicular o N 
bifets 4M ; therefore, yN and NM are 247", 756 each. 
For angle $oN. 
-'9$y 977^, 3 : Radius :: 9 N 247'', 756 : Sine angle 9$60N 
14?41'7'"'.. Addangle NoD = M sU 8° 18' 1s", the fum 
is = angle 96D = $oF = oC = 22° 59’ 22”; the com- 
plement of which is = angle y oC = 67° o' 48". 
For fide Cy = Mercury’s vifible latitude from fun, at the firtt 
external contact. 
Radius’: : OF 977" , 3 :: Sine angle yoC 67° o» 38": Cx 
..899'', 68 = 14" 59", 68; to which add the parallax in lati- 
tude 2”, 867, and the fum 15! 2^, 487 is Mercury's true lati- 
tude by obfervation, at the time of the firít external contact. 
For fide Co, the vifible difference of longitude of the centers of | 
the fan and Mercury, at the time of iie firft external contact. 
— Radius : ©¥ 977, 3 :: Sine angle o¥C 22° 59’ 22" : Co 
= 5 355 696 ; from which fubtra& 2", 224, Mercury's 
parallax 
