C 54° ] 
P. S. In a former letter which I fentyou, I gave, 
by miftake, the error occafioned by aberration lefs 
than I have now given it. The difcovery of this 
miftake I owe to the kind aftiftance and correction 
with which Mr. Mafkelyne, the aftronomer royal, has 
been pleafed to favor me. 
I have, for the fake of more diftin&nefs and clearnefs, 
fuppofed Venus to move in the plane of the ecliptic. 
Some differences will arife from the inclination of the 
path of Venus to the ecliptic, and alfo from taking 
the aberration of the Sun, and the proportion of Venus's 
diftance from the Earth to her diftance from the Sun, 
exaCtly as they really are at the time of a tranfit. Thus, 
at the time of the laft tranftt of Venus, fiippofing light 
to come from the Sun to the Earth in 8', 2, the aber- 
ration of the Sun was The diftance of Venus 
from the Earth was to its diftance from the Sun as 29a 
10726, and therefore the retardation I8': i6 r/ . 
Mr. Canton has obferved, that in the Con . des < Temp fi 
Mr. De la Lande makes the effeCt of aberration at 
the inferior conjunction of Venus and Mercury to be 
an augmentation of their longitudes. Indeed, Mr* 
Blifs himfelf obferves this and yet, through an over- 
ftght, makes the effeCt as to time to be an accelera- 
tion. Vid. Phil. Tranf. vol. LII. p. 249. 
XL VIII. A 
