36$ Mr, Peacock’s Defcriptiom of Inftnments 
FIG. II. (T A B. XIV.) 
As theinffrument, fig. i. proceeds chiefly by finding the po- 
rtions of Points, this is contrived to find the pofitions of Lines, 
and to determine their limits by their reciprocal interfeflions. 
ABOCDE is a compound board, to be placed in a vertical 
pofition. FGHI is the opening, or field of view. KLMN is a 
loofe board, upon which paper is to be fixed ; and the edges of 
the faid board are to be rebated, as defcribed in the plan at zz. 
XYMN and OPQR are grooved recedes, to receive the faid 
loofe board, as occafion may require. STUW is a moveable 
parallelogram, compofed of a rebated frock SU, two like gra- 
duated rulers ST and UW, and the regulating piece TW ; 
the whole connected with ferews, fo as to move freely with a 
fmall force ; and the distances between the centers of motion 
SU or TW to be equal to KF or HQ. i\.E and ED are rebated 
grooves, in which the flock of the parallelogram is to move. 
To nfe the Injirument , 
Having fixed the compound board ABOCDE truly vertical, 
flip the papered board KLMN into the recefs XYMN, or 
OPQR, as the fubieft to be drawn may render firfl neceflary, 
and Hide the flock SU of the parallelogram into the groove AE, 
or ED, to correfpond therewith ; then, by moving the flock in 
the groove with one hand, and at the fame time regulating the 
parallelogram with the other, the top edge of the ruler UW 
may be brought to coincide with any line in the original objeft, 
and the figured divifions on the edge of the ruler will at the 
fame time determine the limits thereof, near enough to avoid a 
confuilon of unneceffary lengths of line, &c. The true repre- 
a fentation 
