rERSPECTIVE. 



The most correct and easy method of drawing an 

 ellipsis is to find the transverse and conjugate 

 axes, and then to complete the curve by a trammel, 

 or by hand. But as it is very difficult to find the 

 transverse and conjugate axes of the ellipses which 

 are the perspective representations of circles, re- 

 course is generally had to anotlier method of 

 obtaining the curve. The circle is circumscribed 

 by a square, as K L M N, in Fig. 3., and the dia- 

 gonals and the lines across the centre, and paral- 

 lel to the sides, are drawn; also the lines, c/, 

 cdy are drawn parallel to the sides, through the 

 points v;here the circle is cut by tlie diagonals. 

 This square, with all these lines drawn across it, is 

 now put in perspective as follows : Draw A B for 

 the horizontal line, and fix B for the centre of the 

 picture, and A B for the distance of the picture. 

 Make D C equal to the width of the square, and 

 draw C B, DB ; draw C A to the distance-point A, 

 cutting ofFDG equal to the depth of the square; 

 then draw G F, parallel to D C, which completes 

 the perspective of the square ; also draw the diago- 

 nal DF. Take now the distances M^/, cN; and 

 transfer them to D .z-, o C ; from these points x and 

 draw lines to the vanishing point B, cutting the 

 diagonals of the square. The points in this reticu- 

 lated square in perspective, which correspond to 

 those in the square KLMN, where the circle 

 passes through, must now be observed, and a curve 

 traced through them with a steady hand : it will 

 be the perspective required. Even in this process, 

 it is of considerable use to know that the curve you 

 are tracing is a regular ellipsis ; for though you can- 

 not easily ascertain the axes exactly, yet you may 

 ^ery nearly ; and the eye very soon discovers 

 whether the curve which has been drawn, be that 

 of a regular elhpsis or not. 



