of the Equatorial Instrument, tji 
for without some competent knowledge of the accuracy of its 
parts, it is in vain to attempt to adjust them, and still more 
so to use them with any degree of satisfaction.- And here the 
chief objects of inquiry have been the accuracy of the divi- 
sions ; the sensibility of the levels ; and the power of the tele* 
scope. I shall begin with the levels ; and first with the axis 
level, P, k, the parts of which may be seen at figure i, 
Tab. XIV. where 1, 2, represent the extremities of the axis 
of the circle of declination ; A, a section of the tube of the te- 
lescope ; 3, 3, the level tube, resting in the cocks or sup- 
porters, 4, 4, and 5, 5, and turning on an axis d, e ; on one end 
of which e, is a toothed wheel g, moved by a small pinion f. 
turned by the screw head b ; and at a, is an adjusting screw 
to bring the level parallel to the axis 1, 2 ; at c is another, to 
bring the level parallel to its moveable axis d, e ; h, is an 
adjusting screw, at right angles to C, to bring the tube of 
the level parallel to its axis d, e ; i, is another screw, to 
make this axis parallel to the axis 1, 2. All these, as well as 
every other adjusting screw throughout the instrument, have 
chamfered heads, with their circumferences divided into 10 
parts, and the value of each ascertained ; so that, by turning 
the screws a whole, or any part of a revolution, the angle of 
motion given to any part may be known. The use of this is 
obvious ; but the degree of convenience is only known to such 
persons as have been conversant with these nice adjustments. 
k and /, are two moveable indexes, to be set to each end of 
the bubble. The tube of this level is about 14 inches long, 
and the curvature of it such, as that by giving it an inclina- 
tion of 15", the bubble moves about ~ inch, and the third or 
fourth part of this space is plainly discernible, so that no 
Ns 
