144 Mr. Wollaston^s Description 
figured accordingly. Hence, supposing the instrument placed 
in the meridian, with the graduated face turned towards the 
east ; if, when the telescope is horizontal and points to the 
south, the upper quadrant nearest to the object-end, be num- 
bered from that end from 1 to go°, with the heads of the fi- 
gures towards the centre of the instrument ; and the other 
upper quadrant be numbered from the eye-end, with the feet 
of the figures towards the centre ; they both would give the 
zenith distances of the objects observed. The former, at mi- 
croscope A, while the telescope points to the south of the 
zenith ; the latter at microscope B, when you are observing 
towards the north. 
The two other, or lower quadrants, follow a similar rule, 
and serve to shew the altitudes, if botli be numbered from the 
quadrature, instead of either end of the telescope ; those lead- 
ing towards the object-end, being placed with their heads, 
while those towards the eye-end, stand with their feet to- 
wards the centre of the circle. 
To render this more intelligible, I will annex a drawing of 
the divisions, (Tab. XVI. fig. 2) numbered indeed only to every 
ten degrees ; though the instrument itself has a figure at every 
degree, that one may always be in the field of view of the 
microscope. Hereby it may be seen, that all on one side of 
the telescope give zenith distances, while all on the other side 
give altitudes ; and yet, that the figures in both the quadrants 
nearest to the object-end are placed with their heads towards 
the centre, and all towards the eye- end with their feet. This 
became necessary ; and though it was a little perplexing at 
first to contrive, and see executed properly, it is found very 
convenient indeed in use. 
