[ 564 ] 
carefully obferved, the longitude may be found from 
thence, without any other obfervations : and this is 
the method propofed by the late Dr. Halley, which 
certainly deferves to be highly efteemed for its great 
fimplicity, and the fmall number of obfervations 
which it requires. Neverthelefs, I muft own myfelf 
of opinion with the learned Abbe De la Caille, that 
it will be more convenient at fea to require the aid of 
more obfervations, which is the method I conftantly 
pradtifed myfelf, during my voyage, having always 
two oblervers, who were ready, one to take the alti- 
tude of the ftar, and the other of the Moon’s upper 
or lower limb, at the inftant I fpoke when I had 
made the obfervation of the diftance of the ftar from 
the Moon. 
I can therefore anfwer, from my own experience, 
both that the method is practicable at fea, and alfo, 
that fo far from being lefs ftmple, it is more fo than 
the other method ; for the additional obfervations that 
it requires are very eafily made, and even the error of 
a degree in the altitudes would feldom be of more 
confequence than an error of a minute, in taking the 
diftance of the ftar from the Moon ; fo that an error 
of i o' or 15' in the altitudes would be of no great 
prejudice : but with refpedt to the facility of the cal- 
culations, there is no comparifon between the me- 
thods, the latter being much lefs intricate, and much 
more concife. The Abbe De la Caille requires the 
altitude of that part of the Moon’s limb from which 
the diftance of the ftar is taken ; but as at fea we can 
only take the altitude of the Moon’s upper or lower 
limb, an allowance might be made near enough, by 
eftimation of the eye, for the difference of altitude 
between 
% 
