THE DOUBLE-COLOURED REFLECTION.
Provide a circular piece of coloured glass, and pierce its centre by means of a common awl, well moistened with oil of turpentine: encircle the glass with the fingers and thumb, hold it in the sunshine or the strong light of a lamp, and the following beautiful effects will be produced. If the glass be red, the luminous spot in the centre will be reflected green; if the glass be green, the spot will be red; if blue, orange; and if yellow, indigo.