"Nay, even if he had wished he could not have done much injury either to me or my friends, because I took good care never to name any of them in my letters: but before I was in prison, and after, I invariably used pseudonyms which were understood by those to whom I wrote. Thus, I called one 'Brother,' another 'Son,' another 'Nephew,' or 'Friend,' and so of their wives, calling this one 'Sister,' that one 'Niece,' or 'Daughter.' In this way no one not in the secret could possibly tell whom I meant, even if the letters had been intercepted, which they never were. I may add that even if the letters had been betrayed and read, they could never have been made further use of by the enemy, in allowing them to be carried to their destination to lure the correspondents on till they should compromise themselves, as was sometimes done. For I never wrote now with lemon-juice, as I once did in the Clink; which letter was betrayed to the persecutor Wade, as I before related. The reason of my doing so then was because there were two letters there, which had to be read in one place, and then carried to another. Now lemon-juice has this property, that what is written in it can be read in water quite as well as by fire, and when the paper is dried the writing disappears again till it is steeped afresh, or again held to the fire. But anything written with orange-juice is at once washed out by water, and cannot be read at all in that way; and if held to the fire, though the characters are thus made to appear, and can be read, they will not disappear; so that a letter of this sort, once read, can never be delivered to any one as if it had not been read. The party will see at once that it has been read, and will certainly refuse and disown it, if it should contain anything dangerous. It was in this way I knew that my letters always reached my friends, and that theirs reached me in safety. And so our correspondence continued, I obtaining sure information of all my friends, and they receiving at my hands the consolation they sought.
"In order, however, that matters might go on still more securely, I managed, through some of my friends, that John Lilly's release should be purchased; and from that time I always got him to bring to my gaoler everything that reached me from the outside. It was through his means too, a little later, that I escaped from the Tower, although nothing certainly was farther from my thoughts when I thus secured his services. All I had in view was to be able to increase my correspondence with safety. This went on for about four months, and after the first month I gave a good time to study by means of books secretly procured. But at this time an event occurred which caused me great anxiety.