"Monsieur Rossignol," said Eliza, "every child knows that the juice of a lime, or a bit of diluted milk, may be used to write secret messages in invisible ink, which may later be made to appear by scorching it before hot coals. When you stare at me in this way, it is as if you phant’sy that some message has been writ upon my face in milk, which you may make visible by the heat of your scrutiny. I beg you remember that more often than not the procedure goes awry, and the paper itself catches fire."