The effect of rippling waves is produced by means of a specially
prepared back cloth. This has a number of slits cut in it (see
illustration). Behind the back cloth is a machine consisting of two
uprights, with a roller-blind attachment at the top, but in place of the
blind there is a large sheet of American cloth perforated in the way
shown in the illustration. Between this American cloth and the back
cloth on the stage is a sheet of prepared gauze. This is necessary,
because the strong light which is used to produce the effect of rippling
waves must be diffused. The light is that of a strong ‘lime’ placed at
the back of the American cloth. Now if the American cloth is pulled up
and down by means of the roller on the upright, the effect of rippling
waves is produced when one looks at the back cloth ‘from the front.’