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LX VII. Ohfervation of the "Tranft (^Mer- 
cury over the Sun, Odlober 25, 1743* 
In a Letter to Projejfor Blifs, late Afro-- 
nomer Royal and F. R. S, from John 
Winthrop, F. R. S. Profejfor of Afro^ 
nomy in Cambridge, New England.. 
Rev. SiRi, 
Read at R. s. > — ^ I V E me leave to lay before yoin 
Nov. 10, 1763, obfervation of the tranfit of 
Mercury, 25 Odober, 1743 j which, if I miftakc' 
not, will determine the longitude of Cambridge,, 
New England, with. more exadnefs than any. of the 
obfervations that have been ufed for that purpofe. 
I adjufted my clock by correfpondent altitudes of the 
bright dar of Aries, taken the night before the tranfit . . 
with a quadrant of two feet radius ; and on the day of 
the tranfit, by correfpondent altitudes of the Sun j alf 
of which agreed within 5''; and allowed for the 
difference of the Sun’s declination, morning andl 
afternoon. 
The morning was fair "and calm, but hazy ; not* 
withftanding which, I had a good view of the Planet,, 
and with a 24 feet telefcope oblerved that 
At 8^ 17' s" ' ^ egrefs touched o ’s limb., 
I S' ^S" went off intirely. 
- Vot. LIX. T t t Icould; 
