[ 8 * ] 
XI. On the Parallax of the Fixed Stars. By Mr. Herfchel, 
F. R. S. ; communicated by Sir Jofcph Banks, Bart. P . R. S. 
O find the diftance of the fixed bars has been a problem 
which many eminent afbronomers have attempted to 
Solve ; but about which, after all, we remain in a great mea- 
fure hill in the dark. Various methods have been purfued 
without fuccefs, and the refult of the fineft obfervations has 
hardly given us more than a diffant approximation, from which 
we may conclude, that the neareft of the fixed bars cannot be 
lefs than forty thoufand diameters of the whole annual orbit of 
the earth diftant from us. Trigonometry, by whofe powerful 
abidance the mathematician has boldly attended into the pla- 
netary regions, and meafured the diameters and orbits of the 
heavenly bodies, for want of a proper bafe, can here be but of 
little fervice ; for the whole diameter of the annual orbit of 
the earth is a mere point when compared to the immenfe dis- 
tance of the bars. Now, as it is not in our power to enlarge 
this bafe, we can only endeavour to improve the inftruments 
by which we meafure its parallax. 
There are two things requifite for measuring extremely 
Small angles with accuracy. Firft, that the inftrument we uSe 
for this purpoSe, be it quadrant, Scdor, or micrometer, fhould 
be divided and executed with Sufficient exadneSs ; and, Se- 
condly, that the telefcope, by which the observations are to be 
Read December 6, 1781. 
made, 
