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becaufe the longitude of the two ftations muft be ri- 
goroufly known, may be pradtifed at both contacts 
in 1769. 
It appears by computation that the time of the firft 
internal contact in the evening is accelerated as much 
as poffible by parallax in 48° 42' of N. latitude, and 
6 to the Eaft of Greenwich, at or near Nancy in 
France. But this computation is framed upon a 
fuppofition that the fun’s center is in the very horizon : 
in which circumftances no obfervation can be taken. 
If the fun’s altitude at the time of the contadt fhould 
be required equal to 5 or 10 degrees, then it will 
appear that Greenwich and Dublin are ftations very 
advantageous ; and we have already feen that the 
time of ingrefs at the former place will happen 7' \ l" 
fooner than if feen from the earth’s center, on 
account of parallax. Indeed the effedl of parallax * 
will be nearly the fame to every part of Great Bri- 
tain. The part of the earth’s furface, where the effedl 
of parallax' upon the planet at the fame contad will 
be as great as poffible in a contrary diredtion, when 
the fun’s altitude is about 5°, is in 46° of S. latitude 
nearly, and in 168° or 169° of W. longitude from 
London, in the great Pacific Ocean, where it does 
not at prefent appear that there is any land. If, how- 
ever, an obferver fliould be Rationed in any of the 
iflahds in the South fea, for which a computation has 
already been made, even in the iflands of Mendoza, 
the morning ingrefs will be found to be retarded by 
parallax 4'' 3 j and confequently a difference at this 
contadt of 11' 43^'' may be obtained by comparing 
the obfervation of the hrfl internal contadt with the 
obfervations at Greenwich ; or i F 24'', if the fame 
obfervation be compared with that at Tornca°. 
5 
In 
