propofed trigonometrical Operation . % i 7 
attempting it, therefore the declination of the ftar fettled for 
any particular period being accurately known *, its apparent 
didance from the pole may, by the edablifhed rules, be readily 
computed for any propofed day, as well as the precife times of 
its greated elongations, twice in 24 hours, when in its eaderu 
and wedern azimuths, at which times it will, for feveral mi- 
nutes, appear, as to fenfe, ftationary or without motion, except 
In altitude. Thefe are, therefore, the bed times for taking 
the angle between the ftar and any particular ftation, {ince the 
obfervations may be repeated frequently in the fpace of a few 
minutes, or until it fhall be perceived that the ftar has again 
approached towards the pole. Now, fuppofe the ftation of the 
indrument to be at Tatterlees , whofe didance from the perpen- 
dicular to the meridian of Greenwich, and confequently from 
its parallel, is known by the trigonometrical operation. The 
latitude of the dation becomes known likewife ; and let the 
co-latitude be 38° 54' 20". Let us likewife fuppofe the didance 
of Bottle-hill on one fide to be 44100 fathoms, equal to 43" 
28". 6 of a great circle; and that of the Brunemberg on the 
other to be 38250 fathoms, equal to 37' 42^.6 of a great cir- 
cle; and further, that on thefe two dations the Indian lights 
are exhibited for the time propofed. Now, let the angle be- 
tween the meridian and Bottle-hill , and that between it and 
the Brunemberg , be obferved by means of the pole dar corrected 
for its didance for the day ; and fuppofe the fird to be 75 0 10', 
* Since this Paper was written, the Aftronomer Royal has been fo obliging a* 
to furnifli me with the mean diftance of the pole ftar from the pole, as fettled at 
Greenwich by eight obfervations above and nine below it, made in the year 
1786; whereby it appears, that the mean diftance, reduced to the beginning of 
that year, was 1° 50' 8". 35; and the mean annual preceftion in declination 
being 19". 55, confequently, the mean diftance for the ift of January, 1787, 
was i° 49' 8". 8. 
Vol. LXXVII. F f and 
