140 Gen. Roy’s Account of 
adapted for the fame purpofe. This laft may be feen attached 
to the curbs, as reprefented towards the right hand of Plate V. 
It confifts of a brafs cock, fixed to, and projecting outwards 
from, the curb of the inftrument ; which cock is aCted upon 
by two fcrews working on the oppofite tides againft it, and 
which are clamped to the curb of the oCtagon. 
Art. VII. Mahogany Balujlrade and Cover . 
The curb, whereon the three feet of the inftrument reft, 
carries a baluftrade of mahogany fitted to receive, on the top 
thereof, a mahogany cover, no where reprefented except in the 
two feCtions in Plate IV. In this cover there are only four 
imall openings (betides that which allows the great vertical 
axis to pafs), viz . one for each vertical microfcope, one for the 
clamp of the circle, and one for the focket of the Hook’s-joint, 
The two laft are lefs than the former. At the fame time that 
this cover effectually fecures the circle with its cones from dirt 
and from accidents, it ferves conveniently for laying the Hook’s- 
joint upon, or any thing that may be conftantly wanted near 
at hand ; but more particularly for placing the lanterns ufed at 
night for reading off the divifions on the limb of the inftru- 
ment that come immediately under the vertical microfcopes. 
Art. VIII. Achromatic Telefcopes. 
Two achromatic telefcopes, each of thirty-fix inches focal 
length, with double objeCt-glaffes of two inches and a half 
aperture, belong to the inftrument. They are excellent of 
their kind, and are furnifhed with eye-pieces of different mag- 
nifying powers, for ereCt as well as inverted vifion. The lower 
telefcope lies exaCtly under the center of the inftrument, and is 
direfted through one of the openings of the baluftrade. Being 
only 
