finding ’time by equal Altitudes. 93 
making the inftrument follow the object in its motion in - 
azimuth, without danger of difturbing its adjuftment in 
regard to altitude. 
To remedy all thefe inconveniencies, the following 
method was thought of ; and having been pradtifed with 
conftant fuccefs, it is prefumed, the communication of 
it may be acceptable to aftronomers. 
If a ftar is feledted, of which the polar diftance is very 
little lefs than the complement of the latitude of the 
place of obfervation, it will, at equal diftances from the 
meridian, come to vertical circles, which touch its 
parallel of declination. The ftar, when in thefe ver- 
tical circles, will be near the meridian, near the prime 
vertical, and near the zenith ; and confequently, if it be 
obferved there, the interval between the Eaftern and the 
Weftern altitudes will be fhort; the alteration in altitude 
will be quick ; the ftar cannot be affeCted by a different 
refraction; beftdes, it will have no motion in azimuth. 
To obferve the ftar in thefe vertical circles, two things 
are neceffary ; the firft is, to be provided with an aftro- 
nomical quadrant, having three or more horizontal 
wires in the telefcope, and if it have alfo a fpeculum at 
the eye-end of the telefcope, to bring the vertical ray 
horizontal, it will be found very convenient. The 
next thing is, to make a computation of the apparent 
zenith diftance of the ftar in the vertical circles which 
touch its parallel of declination; for if the telefcope 
be fixed to this zenith diftance, as foon as the ftar is 
found 
