Page:An introduction to linear drawing.djvu/81

 ﻿the next figure illustrates the rules for drawing a circle in perspective.

tig. 7. plate ii.

Draw the Circle and enclose it in a square. Draw parallels to the sides of the square where the diagonals cut the circle, then a parallel to the sides passing through the centre of the circle. From the points, where these parallels strike the base line, lead off vanishing lines to the vanishing point. Follow the directions given in fig. 5, for completing the squares ; but the circles must be drawn by the eye through the eight points formed by the intersection of the diagonals and vanishing lines. Of course, more vanishing lines may be made if the circle be large, and they are necessary.

It will be noticed,that in this figure one half of the lines is dotted. Thejobject of this is to show that, in drawing the arches of a bridge in perspective, the easiest way is to draw circles, the arch being half of a circle, and represented in the figure by the lines not dotted, the prime vertical line representing the surface of the water.

This figure may serve also to show the perspective of a Rhomb or Lozenge, represented by the diagonals of the squares. The Piers of the bridge deform the second rhomb, but, if no space be left between the squares or circles, the rhomb will be perfectly formed.

fig. 8. plate ii.

From the five angles of the Polygon, draw as many perpendiculars to the base line, and let the left hand perpendicular extend far enough down to intersect hor- izontal lines from the five angles abovementioned. Then from the points where the five perpendiculars strike the base line, lead off five vanishing lines to the vanishing