C *7* ] 
by the horizontal wire of the telefcope, till the body 
paffes the middle vertical wire, and carefully note the 
time of its paffage; there leave the telefcope fixed as 
to altitude, and releafing the horizontal motion, 
turn it round on it’s vertical axis, till you meet with 
fome ftar, that in a little time after will by riling or 
falling come to the fame almicanther ; and, on it’s 
arrival, carefully note the time of it’s pafifage crofs the 
horizontal hair of the telefcope. 
Now, from the right afcenfions and declinations 
of the two ftars being previoully known, or after- 
wards determined from meridian obfervations ; the 
azimuth of the firft ftar, and the altitude of the laft, 
at the time of their refpe&ive paflages, may be de- 
termined by computation ; which will give the altitude 
and azimuth of the heavenly body, for the time of 
the middle obfervation, when it palled the interfe&ion 
of the two wires. 
The fame end may alfo be obtained by taking the 
obfervations in an inverted order ; that is, by chufirtg 
a fiar at fuch an altitude, that the heavenly body fhall 
in a competent time afterwards arrive at the fame 
altitude, &c. but, asinthefe latitudes the alteration of 
azimuth is, efpecially in thofe parts that are in the 
neighbourhood of the zodiack, quicker than that of 
altitude, I apprehend it to be eafier to follow the 
flower motion with the fcrew, fo as to prefei ve the 
interfecftion, than the quicker, and therefore in ge- 
neral to be preferred ; but where it happens other- 
wife, or the ftars lay more conveniently, the inverfe 
method may be purfued. 
It is true, that fome degree of dexterity and 
practice may be requifite in the obferver in managing 
Z 2 the 
