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XX 11. Sketches and Defcriptlons of three Jlmple Injlruments for 

 drawhig Arch'itediure and Mcichinery hi PeffpeSiive. By Mr* 

 James Peacock ; cotmrnmicated by Robert Myltie, Efq» F.R.S, 



Read March 17, 1785. 



i- 



OME of the following machines muft be placed upon the 

 front edge of tlie table upon which they are to ftand. 

 The fights may befupported by a three-legged ftafF. 

 The ftocks of the fquares or indexes may have fteel fprings 

 upon their edges, in order to keep them in any affigned part of 

 the grooves in which they are to Aide. 



F I G. I. (t AEi XIII.) 



ABCD a drawing board, to be fixed on a table or ftand, &c, 

 in a vertical pofition. AB a fliding-piece for the top of the T 

 fquare, having a rebate therein to form a groove, as expreffed 

 by the dotted line. CD, fliding-piece for the bottom of the fquare, 

 having a rebate therein to form a groove for the reception of 

 the ftock as defcribed by the dotted line ; this fliding-piece to 

 be of fufficient length to receive and fupport the faid ftock 

 when the blade of the fquare is coincident v/ith the lines 

 KNFH or LNGI. E a hole to receive the arm or Aider of the 

 fight-piece, to be ccnftrucled in the ufual manner. FGHI an 

 opening forming the field of view for the prototype. KLMNT a 

 iheet of paper fixed on the upper part of the board for the 

 •^copy, the four inner lines whereof form and inclofe a fpace of 



the; 



