Dissolve a small lump of indigo in sulphuric acid by the aid of moderate
heat, and you will obtain an intense blue colour; add a drop of this to
half a pint of water, so as to dilute the blue; then pour some of it
into strong chloride of lime, and the blue will be bleached with almost
magical velocity. This trick is called “The Restoration”—of the Bourbons
understood, since their colour, the Royalist white, replaces the
Republican blue.