C 481 ] 
ing obfervations made at Paris, the Cape was found 
by the Abbe de la Caille himfelf to be to 
the E aft of Paris, or i h .i 3 '.3 1" to the Eaft of Green- 
wich. Mafon and Dixon obferved many 
eclipfes of Jupiter’s Satellites at the Cape, but the 
weather was not fo favourable here in England. 
However by comparing four obfervations made in Sur- 
ry-Street and one at Greenwich with thofe made at 
the Cape, the difference of longitude at a mean is 
found to be i h .i3'.2 8' , which I have ufed in the fol- 
lowing computations. 
The internal contact, as reduced from fiderial to 
appaient time by Mr. Mafon, happened at 
2lh - 3 9 '- 5 2 "- — But upon examination it will be 
found to have happened later : for whether we make 
ufe of the Sun’s mean R. afcenfion from the bed: folar 
tables extant* or the Sun’s apparent R. afcenfion 
reduced to the meridian of the place as determined 
by adtual obfervation on the day of the tranfit, the 
true apparent time of the contaft will be found to have 
happened at 2i h 2g'.^4. or at 2 \L if the 
time by the Ear Antare.s be ufed, wbofe fituation was 
more favourable to an oblerver in 34 0 . of South lati- 
tude. I fhall therefore fuppofe the internal contact to 
have happened at 2i I \ 39 / .52 // by taking a mean of 
the two obfervations 
The Royal Obfervatory at Paris was fuppofed by 
Sir Ifaac Newton, in his Principia, to be g'.2o" to 
the Eaft of Greenwich. And the editor of Dr. Hal- 
* Mr. Mafon, before heleftEngland, acknowledged, inalettcr 
to me, that he had committed a miftake in his calculation, by 
iorgetting to apply to the Sun’s place the equation of pneceffion, 
which on the clay of the tranfit amounted to 15A6. 
1 ley’s 
