C Si8 ] 
taking a medium between all the obfervations of each 
aftronomer. But I have not always found, that the 
different obfervations of other afironomers agree fo 
well with each other, as yours do : For which reafon, 
I have been a little more doubtful in concluding the 
true parallax of the Sun ; and I have no hopes of be- 
ing able to determine it more precifely, than I have 
done from your obfervations, till I have verified the 
obfervations of all the other afironomers by each 
other, and rejected thofe, which fhall be found evi- 
dently faulty, after a rigorous examination of them, 
which I intend to make. 
I have not yet compared your other obfervations 
with thofe of Monfieur de la Caille : 1 propofe to do 
it, as foon as I fhall have leifure. I fend you, in the 
mean time, his obfervations, which our Academy has 
publifhed, in order to give other afironomers the fa- 
tisfadlion of comparing them with their own. 
I do not doubt, that you, Sir, have thought of the 
tranfit of Mercury over the Sun, expedled on the 6th 
of May next year. I have made a calculation of it 
from Dr. Halley’s tables, redlified, not only by cor- 
rections given by himfelf after the tranfit in 1723, 
but likewife from the obfervations made upon the 
tranfit in 1740, at Cambridge in New England ; fo 
that I hope to be exadt within a few minutes, with 
refpedt to the ingrefs and emerfion of Mercury into 
and from thedifkof the Sun. 
I have calculated, that the ingrefs will be at 2 h 44/ 
in the morning at Paris, and the emerfion at io h 37 
and, confequently, the duration of the palfage 7 11 53' j, 
and, likewife, that Mercurv will pafs near the centre 
of the Sun ; which is lulhcient to inform the afiro- 
nomers. 
