Wheatstone's photometer was probably suggested by this appliance. The photometer enables two lights to be compared by the relative brightness of their reflections in a silvered bead, which describes a narrow ellipse, so as to draw the spots into parallel lines.[citation needed]
There are several different versions of the kaleidophone, but in all cases at least one slender rod is fixed at one end and has a shiny bead fixed to the other end of the rod. As the rod vibrates the spot is seen to describe Lissajous curves in the air, like a spark whirled about in the darkness.[2]
