OPALUS.	247
	The mode of cutting this very fragile stone is first upon a leaden plate coated with adoucis (emery-powder that has been already used upon other gems, and so deprived of its asperity) ; next on a wooden wheel with fine pumice-powder; finally on a third covered with felt moistened. The last polish is given with a cloth and tripoli. The Musée de Minéralogie, Paris, possesses a very fine Opal carved into a bust of Louis XIII., when a child—a piece of unreasoning extravagance, where work and material mutually destroy each other's beauty and value : the iridescence entirely neutralising all effect of light and shade in the relief.