C 8i 1 
vata are fixed in a vertical brafs circle, of the breadth and 
thicknefs of two-tenths of an inch, and of fuch a dia- 
meter, as to allow the circle of inclination and the paral- 
lelogram to move freely round within it. This fecond 
circle I fhall call the general meridian. It is not gra- 
duated, but has a fmall brafs weight fixed to the lower 
part of it, to keep it upright; and the circle itfelf is 
fcrewed, at rjght angles, into another circle, of equal in- 
ternal diameter, of the fame thicknefs, and twice the 
breadth, which is filvered and graduated on the upper 
fide to every half degree. It reprefents the horizon, as 
it fwings freely upon gimbols, and is always nearly par- 
allel to it. The whole is contained in a neat mahogany 
box, of an o<Stagon figure, with a glafs plate at top and 
one on each fide, for about two-thirds down. That part 
of the frame which contains the glafs lifts off occafi- 
onally. The whole box turns round upon a ftrong brafs 
center, fixed in a double plate of mahogany, glewed to- 
gether crofs-ways, to prevent its warping or fplitting; 
and this again is fupported by three brafs feet, fuch as 
are ufed for the cafes of table knives, frofted that they 
may not eafily flip, if the veffel fhould have any confi- 
derable motion. It has another fquare deal box to lock 
it up in, to preferve the glafs, 8cc. when it is not wanted 
for ufe. 
The ufe of this inftrument is very plain', as the incli- 
nation or dip is at any time apparent from infpe6lion 
only, and alfo the variation, if the frame is turned round 
till the great vertical circle lies exadUy in the plane of 
VoL. LXV. M the 
