[ 5 61 ] 
the plane of the quadrant, the Moon was feen entirely 
by reflexion from the unfoiled part of the fpeculum, 
which I generally found to be the moft convenient : 
for my part, I fhould always recommend the ufing of 
a fmall telefcope, magnifying about three times, as it 
would make the objedts appear more didindt, and ren- 
der the contadt of the dar with the Moon’s limb more 
evident. 
My telefcope, which was about 6 incles long, con- 
fided of two convex glades, fo that it inverted ob- 
jedts ; which is of no fort of inconvenience to people, 
who have been ufed to inverting telefcopes, the prac- 
tife of which is foon acquired. But if any one would 
rather chufe to have a telefcope that fhews objedts in 
their natural pofition, he may ufe one confiding of a 
convex objedt-glafs and a concave eye-glafs ; which 
kind of telefcope anfwers better in fhort lengths than 
the other. 
Before I deliver the procefs of the computation of 
the longitude, I fhall fird fay fomething with refpedt 
to the obfervations themfelves, and mention fome 
cautions concerning them. 
A mod particular attention mud be paid to the 
exadt adjudment of the quadrant, as a thing of equal 
confequence with the obfervation of the didance of 
the dar from the Moon. This is fo much the more 
neceflary, as the adjudment is fubjedt to alter fen- 
fibly, even from one day to another. The bed 
objedt of all for this purpofe is the horizon of the 
fea, when clear j and I found it mod convenient, in 
this cafe, not to ufe the telefcope, but applied a con- 
cave glafs to my eye, which was fitted for giving 
4C2 
