This substance, obtained from the shell of the pearl oyster, is much
admired for the fine play of its colours. To observe them accurately,
select a plate of regularly formed mother-of-pearl, with its surface
nearly parallel, and grind this surface upon a hone, or upon a plate
of glass, with the powder of slate, till the image of the candle,
reflected from the surfaces, is of a dull reddish white colour,
when it will glow with all the colours of the rainbow. The colours
of mother-of-pearl may be communicated to soft black wax; and to
clean surfaces of lead and tin by hard pressure, or the blow of a
hammer. Or, dissolve gum arabic, or isinglass, in water, and allow
it to harden upon a surface of mother-of-pearl, when it will take
a perfect impression from it, and exhibit all the colours in the
finest manner. Or, place the isinglass between two finely-polished
surfaces of mother-of-pearl, and you may obtain a film of artificial
mother-of-pearl, which, when seen by the light of a candle, or by an
aperture in the window, will shine with the brightest hues.