_Brown._—Soak the stone in a solution of silver in spirits of nitre, dry
in the sun, then put in a damp place, and on again exposing it to solar
light, the colour will appear. Repeat to deepen shade.
_Light Brown._—A solution of gold.
_Gray._—Add to the silver solution a quarter of its weight of lard and
red tartar.
_Deep Violet._—Add to the silver solution some plumose alum.
_White._—The action of bismuth bleaches it so that it looks white; it
will appear pale brown in the shades.
_To draw Figures on the Stone._—Rough it, write with a quill, and the
silver solution will dry it quickly.