[ 4 8o ] 
Hope : for by comparing the obfervations made there 
with thofe at Tornea 0 , Tobolfki, and in fome of the 
Eaftern parts of Alia, the difference of the times of 
the contacts when reduced to the fame meridian will 
be found to be very confiderable, amounting to more 
than 9 ^minutes at the two firft places above mention- 
ed, and being greater, as the places are farther litu- 
ated to the North-Eaff But if this method be uled, 
it is abfolutely neceffary that the longitudes of the 
places Ihould be determined with the utmoft accuracy, 
iince an error of a few feconds would have a confi- 
derable influence upon the refult, and would increafe 
or diminifh the quantity of the Sun’s parallax, in pro- 
portion. The unfavourable flate of the heavens at 
the time of the internal contadt prevented the Rev. 
Mr. Mafkelyne from making an obfervation at the 
Iile of St. Helena ; which is the more to be lamented 
as his obfervation would have confirmed or corredted 
the obfervation at the Cape, if neceffary ; fince the 
effedt of parallax at both places would have been 
very nearly the fame. The obfervers at the Cape 
were more fortunate, and differed only 4/' in their 
obfervation of the internal contadf . — But before we 
proceed to deduce the quantity of the Sun’s parallax, 
by comparing as well the obfervation made at Green- 
wich as thofe at other places, with the obfervation at 
the Cape, it will be neceffary to lay before the reader 
the authorities upon which the longitude of each 
place has been determined. 
The longitude of the Cape of Good-Hope was 
not even nearly known till the Abbe de la Caille 
went thither in the year 1751. By a companion of 
9 eclipfes of Jupiter’s fatellites as well immer lions as 
emerlions obferved at the Cape with the correfpond- 
ing 
