5^(3? Mr. Peacock's Defer ipt ions of Injlruments 



to this, two fquare boards are to be provided, equal in fize, and 

 cf fimllar conil:ru6lIon ; one is to be fixed in a vertical poiition, 

 for viewing the original object through a proper aperture ; and 

 the oiher is to be laid flat upon a deik or table, for the greater 

 cafe and conveniency of drawing the copy upon paper to be 

 fixed thereon for that purpofe. 



ABCD is the vertical board ; EFGH the opening therein, 

 forming the held of view ; IKL the T fquare, the blade 

 thereof PL being moveable about the center P, wltii a mode- 

 rate degree of ftiffnefs ; the flock K is to (lide in a rebated or 

 dove-tail groove AD, and be fixable to any part thereof by th^ 

 fcrew O ; the fteel points MN are to move with moderate eafe 

 in a rebated or dove-tail brafs groove in the middle of the 

 blade of the fquare ; upon the back of the groove AD are to be 

 fixed two brafs pins QQ, to refh in proper holes, funilar to- 

 the holes marked RR; and the fame kind of holes are to be made 

 in the corner of the board whereon the copy is to be made. 



To ufe the Machine. 



Having placed the board ABCD in a truly vertical poiition', 

 fix the fhifting groove AD in the rebate, on the moft conve- 

 nient j(ide of the board, by means of entering the pins Q^into 

 the holes R ; then loofen the fcrew O, and move the flock 

 IK, and at the fame time turn the blade PL upon its center P, 

 until one of its edges fhall be coincident with fome original 

 line ; then fix the ftock by turning the fcrew O ; move the 

 points M and N, till they exa£lly include the apparent length of 

 the faid line ; then take off the fhifting groove AD, together 

 with the T fquare or bevll fixed thereto, and apply the fame to 



the 



