DESCRIPTION OF A PERSPECTIVE INSTRUMENT. C 2&3 



to form a tafte for the fine arts ; it may, however, be carried 

 to excefs. There are improvers who prefer the mod dreary 

 rain to an elegant and convenient manfion, and who prefer a 

 blafled Mump to the glorious foliage of the^oak. 



" Perfpective is not, however, recommended merely as a Young perfons 



r . . , ,, , , ., . r r i ' r -vj. i' who underftand 



means ot improving the talte, but as it is uietul in facilitating pet f pe ^j ve ma y 

 the knowledge of mechanics. When once children are fami- acquire much 

 liarly acquainted with perfpective, and with the reprefenta- k^edge from 

 tions of machines by elevations, fections, &c. prints will fup- drawings, 

 ply them with an ex'tenfive variety of information ; and when 

 they fee real machines, their Itructure and ufe will be eafily 

 comprehended. The noife, the feeming confulion, and the 

 iize of feveral machines, make it difficult to comprehend, and 

 combine their various parts, without much time, and repeated 

 examination ; the reduced fize of prints lays the whole at once 

 before the eye, and tends to facilitate not only comprehenfion, 

 but contrivance. Whoever can delineate progreflively as he 

 invents, faves much labour, much time, and the hazard of 

 confulion. Various contrivances have been employed to fa- 

 cilitate drawing in perfpective, as may be feen in '* Cabinet 

 de Ser\ ier, Memoirs of the French Academy, Philofophical 

 Transactions, and lately in the Repertory of Arts.-" The fol- 

 lowing is fimple, cheap, and portable. 



" Plate XVI. Fig. 1. A, B, C, repre'fent three mahogany Defection of 

 boards, two, four, and fix inches long, and of the fame the inftrument 

 breadth refpcctively, fo as to double in the manner reprcfen- po ] nts jn per - 

 ted. Fig. 2, the part A is fcrewed, or clamped to a table of fpe&ive views, 

 a convenient height, and a Aieet of paper, one edge of. which 

 is put under the piece A, will be held fail to the table. The 

 index P is to be fet (at pleafure) with its lliarp point to any 

 part of an object which the eye fees through E the eye-piece. 



" The machine is now to be doubled as in Fig. 2, taking care Tts ufe, 

 that the index is not difiurbed ; the point, which was before 

 perpendicular, will then approach the paper horizontally, and 

 the place to which it points on the paper mtift be marked with 

 a pencil. The machine muft be again unfolded, and another 

 point of the object is to be afcertained in the fame manner as 

 before ; the fpace between thefe points may be then connected 

 with a line ; frefh points Ihould then be taken, marked with a 

 pencil, and connected with a line j and fo on fucceffively till 

 Uie whole object is delineated." 



The 



