384t PERSPECTIVE. 



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 another 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, at, 

 cd y are drawn parallel to the sides, through the 

 points where the circle is cut by the 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 D F. Take now the distances M a, c N ; and 

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

 o 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 

 very nearly ; and the eye very soon discovers 

 whether the curve which has been drawn, be that 

 of a regular ellipsis or not. 



