Mr. a u bert’s Method of 
IV. A new Method of finding ’Time by equal Altitudes. 
By Alexander Aubert, Ffq. F. R. S. 
R. Nov. 9, Jk MONO the various methods practifed for 
I77j jTJl finding time, that by equal altitudes of 
the Sun or of a ftar, hath hitherto been efteemed the moft 
eligible for obfervers who are not furnifhed with a good 
and well-adj ufted tranlit inftrument. But this method, 
although one of the beft, is generally attended with in- 
conveniencies, which render the practice of it more dif- 
ficult, and the refult lefs perfect than one could wiffi. 
If the Sun or ftars near the equator are made ufe of,, 
as ufual, and the altitudes are taken near the prime ver- 
tical, where the change of altitude is the quickeft, the in- 
terval of time between the obfervations mttft, in moft; 
latitudes, be of fo many hours, that the obferver cannot 
always attend to the correfponding altitudes : the weather 
may prove variable, fo as to difappoint him at laft; the 
clock or watch may go irregularly during fo long an in- 
terval ; and if the altitudes cannot, on account of their 
great diftance from the meridian, be taken very high; 
an alteration in the ftate of the atmofphere may produce 
a variation of the refraction, and occafion the horary 
arcs to be different, although the apparent altitudes will 
be the fame. To which may be added, the difficulty of 
making 
