Page:The wonders of optics (1869).djvu/226

218 ous, according to the position in which the mirror is hung. Such distortions are known to opticians as anamorphoses, from two Greek words signifying the destruction of form; and distorted drawings used to be sold at one time which when reflected from the surface of the cylindrical mirror, became perfectly symmetrical. Anamorphic drawings may be also made, which when looked at in the ordinary manner appear distorted, but when viewed from a particular point have their symmetry restored to them. With a little knowledge of drawing, it is not difficult to produce these in great variety.

Suppose the portrait in fig. 62 to be divided horizontally and vertically by equidistant lines comprehended within the square.



Upon a second piece of paper draw the figure shown in fig. 63 in the following manner. Draw the horizontal line a b equal to (fig. 62,) and divide it into the same number of parts. Through the centre draw a perpendicular line to, and cross it by a line e d parallel to a b. Lastly, draw horizontal to e d. The length of the two lines e and  is quite arbitrary, but the longer you make the former in proportion to the