[ 41 ® ] 
level Rings E *>,then is the Inftrument corre&ly trimm’d ; 
if they appear much above or below the Rings, move 
the Tubes a little up or down, till the Surfaces are 
adjufted to the Rings* which is effected by means of 
the regulating Screw /, fix'd at the End of the Bafe 
Tube. 
As I well know theFondnefs our Navigators have 
to ‘Davis’s Quadrant, I adapted the Apparatus to this 
Inftrument, which is fo far from being perplexing, 
that it becomes obvious at firft View, and by which 
an Obfervation can be made with great Facility 5 for 
the Obferver may place himfelf in the moft conve- 
nient Part of the Ship, where there is the leaft Mo- 
tion and Wind todifturb him, and fitting on a Stool 
or the Deck, holding the Inftrument with his left 
Hand under the horizon Vane Ez , and his Right at 
the End of the Label F y with his Thumb thereon, 
keeping the Label on the fame Height or Level with 
his Eye, bring the left convex Surface of the Mercury 
to appear juft vifible above the central Ring E , and 
the Shade or Speculum of the Sun from the Solar 
Vane k , to coincide therewith on the central Line 
Ez 5 and the Sum of Degrees and Minutes cut on the 
two Arches by the Vane k , and the End of the Label 
F, will give, as ufual, the Angle of the Suns Co- 
altitude. As the Sun rifes, the Shade will fall below 
the central Line (the Surface in its proper Place) j and 
when it pafles the Meridian, and falls, it will appear 
above, fo that the End of the Label muft be moved 
in the fame manner as the Sight Vane ufually is. 
To obferve by a Star, another Perfon muft look 
through the Slit on the Horizon Vane, and over the 
upper Edge of the Shade Vane, and bring the Star to 
coincide 
