258 Mr. Bowditch on the Longitude of Cambridge. 
On the longitude of Cambridge University. 
The laté Rev. President Willard, in volume i. page 60 of the 
Memoirs of the American Academy of Arts and Sciences, made the 
difference of meridians between Greenwich and Cambridge 4A. 44’ 
30”2, by the mean of the observations of the solar eclipses in 1766 and 
1778, and the transit of Mercury in 1743. In these calculations he 
supposed the difference of meridians between Greenwich and Paris to 
be 9‘ 16” in time instead of 9'21", which is now used by astronomers.* 
This causes a difference of 5” in the longitude of Cambridge, dedue- 
ed from the transit of 1743. The ratio of the polar to the equatorial 
diameter of the earth was assumed. to be 222, whereas the latest cal- 
culations of Burg and La Place, from the lunar equations arising 
from the oblate figure of the earth; make it $24, or nearly 222; as sup- 
posed by La Lande. For these reasons I concluded to recaleulate 
these and other late Nnadwiieaviank the new tables of Burg, De- 
lambre, and La Lande, as published in the third volume of Vinee’s As- 
tronomy, always using the ratio of the diameters of the earth as as- 
seamed by ‘La Lande, $f Fi 3 2 Se eS oe 
The first observation calculated by President Willard is an celipse 
of the sun of Aug. 5, 1766, at Greenwich, in the latitude of 51° 28’ 
a = by Dr. Maskelyne and his assistant. The mean of 
: pie <2) be 
ae a site. in the third edition of his Astieecan, supposed the di: : 
of meridians of Greenwich and Paris to be 9’ 18’”-8, in conformity to the « calcu, 
lation of General Roy, from the survey made some years ago for connecting the. 
two observatories, (Vide Phil. Trans. 1790, page 223,) A more accurate es 
timate from the same data by Mr. Dalby, made it 9’ 20”-4. (Phil. Trans. 1791, 
Part 2, p. 245.) Delambre, in his Solar Tables, published in a 
the difference of meridians to be 9’ 21”. ; at ipa 
