* 
finding 'Time by equal Alii hides. 
field of the telefcope; and if the vertical wire is once 
brought near to the ftar, the ftar will appear to move 
parallel to it, and will pafs fucceffively over tire horizon- 
tal wires, while the inftrument remains undifturbed. 
The advantage of this method will appear in the fol- 
lowing example of equal altitudes, taken the 15 th July, 
1773, at Loam-pit Hill, near Deptford, in latitude 
5 i° 28' 7" N. and longitude 5" in time W. of the Royal 
Obfervatory at Greenwich. 
The ftar feleCted was y Draconis, having 38° 28' 21 7 
apparent North polar diftance, being very little lefs than 
the complement of the latitude 38° 3T 53". 
Then cof. pe : rad. :: cof. pz : cof. ze — 2° 19' the zenith diftance, 
and fin. pz : rad. :: fin. pe : fin. pze zr 87° 5.' 20 " the azimuth, 
/ yy 
alfo rad. : tan. fe :: cotan. Pz : cof. zpe — 3 0 43' 13" the horary arc zc 14 52,9 
The true zenith diftance being 2° 19', the fame was 
diminillied by 2" for refracftion, and the telefcope fixed 
to 2 0 1 S' 5 8", the apparent zenith diftance ; and when the 
ftar came to the wires, the times by the clock were as fol- 
low; 
Eaftern altitudes, Weftern altitudes. Meridian paflage. 
fo that in about 34' the compleat fet of altitudes was ob- 
tained near the prime vertical, free from the effects of a 
different refraction, and any motion in azimuth. The 
in fidereal time, or 14 50,5 in mean time. 
h 
// 
10 12 44 >S 
10 12 44,5 
10 12 44,5 
horary 
