E 5» 3 3 
XXXIII. A Letter from Jofeph Willard to the Rev , Dr. 
Mafkelyne, Aftronomer Royals concerning the Longitude of 
Cambridge in New England, 
Read July 5, 1781. 
ft E V. SIR, 
r IWHE difference of meridians between Greenwich and 
1 Cambridge has been generally reckoned 4I1. 44k This 
was what the late Dr. winthrop made ufe of; but I do 
not find that he determined it by actual obfervations, made by 
him at Cambridge, compared with correfponding ones, made 
.at the Royal Obfervatory at Greenwich. It appears, that in 
1769, at the time of the trail fit of Venus, the do&or was not 
entirely certain of the longitude of Cambridge. He mentioned 
4 h. 44' as near the truth ; but for better fixing it, he gave 
feveral of his obfervations of the eclipfes of Jupiter’s fatellites 
to be compared with thofe made at Greenwich;; but there were 
too few correfponding ones to determine the point with preci- 
fion ; and as modern aftronomers do not make abfolute depen- 
dence upon the difference of meridians deduced from the eclipfes 
of Jupiter’s fatellites, unlefs there has been a feries of obfer- 
vations, both of immerfions and emerfions, I have wifhed to 
find fome obfervations of folar eclipfes and occultations of fixed 
ftars by the moon, made at Cambridge, of which correfpond- 
ing ones were made at Greenwich. I have met with no obfer- 
wations of occultations made by Dr. winthrop; but a folar 
o eclipfe 
