A Secret Correspondence By Means Of Invisible Ink
A person wishing to carry on a correspondence with another, and who is
fearful of having his letter opened, or intercepted, can adopt the
Write any unimportant matter with common ink, and let the lines be
very wide apart: then between these lines write the communication you
wish to make, with any of the above invisible inks you can most
Your correspondent is to be previously apprized of the method of
making the characters visible: and writing in common ink will serve to
lull the suspicions of those who might intercept the letter, and who,
not finding any thing important in it, will either forward or keep it.
In either case there can be no danger, as the writing will not be
visible without the proper application.