After looking over them carefully I settled quietly down to a minute examination of them. I felt instinctively that my mandate or commission was to see if they contained any secret writing. The letters I placed aside, for the present at any rate. They were transparently simple and written in a flowing hand which made anything like the necessary elaboration impossible. I knew something of secret writing, for such had in my boyhood been a favourite amusement with me. At one time I had been an invalid for a considerable period and had taken from my father’s library a book by Bishop Wilkins, the brother-in-law of Oliver Cromwell, called “Mercury: or the Secret and Swift Messenger.” Herein were given accounts of many of the old methods of secret communication, ciphers, string writing, hidden meanings, and many of the mechanical devices employed in an age when the correspondence of ambassadors, spies and secret agents was mainly conducted by such means. This experience had set my mind somewhat on secret writing, and ever after when in the course of miscellaneous reading I came across anything relating to the subject I made a note of it. I now looked over the papers to see if I could find traces of any of the methods with which I was acquainted; before long I had an idea.
It was only a rudimentary idea, a surmise, a possibility; but still it was worth going into. It was not any cause of undue pride to me, for it came as a corollary to an established conclusion, rather than as a fine piece of reasoning from acute observation. The dates of the letters gave the period as the end of the sixteenth century, when one of the best ciphers of that time had been conceived, the “Biliteral Cipher” of Francis Bacon. To this my attention had been directed by the work of John Wilkins and I had followed it out with great care. As I was familiar with the principle and method of this cipher I was able to detect signs of its existence; and this being so, I had at once strong hopes of being able to find the key to it. The Biliteral cipher has as its great advantage, that it can be used in any ordinary writing, and that its forms and methods are simply endless. All that it requires in the first instance is that there be some method arranged on between the writer and the reader of distinguishing between different forms of the same letter. In my desk I had a typewritten copy of a monograph on the subject of the Biliteral cipher, in which I half suggested that possibly Bacon’s idea might be worked out more fully so that a fewer number of symbols than his five would be sufficient. Leaving my present occupation for a moment I went and got it; for by reading it over I might get some clue to aid me. Some thought which had already come to me, or some conclusion at which I had already arrived might guide me in this new labyrinth of figures, words and symbols.[1]
When I had carefully read the paper, occasionally referring to the documents before me, I sat down and wrote a letter to Miss Anita telling her that I had undertaken the task at once on her suggestion and that I surmised that the method of secret writing adopted if any, was probably a variant of the Biliteral cipher. I therefore sent her my own monograph on the subject so that if she chose she might study it and be prepared to go into the matter when we met. I studiously avoided saying anything which might frighten her or make any barrier between us; matters were shaping themselves too clearly for me to allow myself to fall into the folly of over-precipitation. It was only when I had placed the letter with its enclosure in the envelope and written Marjory’s—Miss Anita’s—name that I remembered that I had not got her address. I put it in my pocket to keep for her till we should meet on Tuesday.
When I resumed my work I began on the two remaining exhibits. The first was a sheaf of some thirty pages torn out of some black-letter law-book. The only remarkable thing about it was that every page seemed covered with dots—hundreds, perhaps thousands on each page. The second was quite different: a narrow slip of paper somewhat longer than a half sheet of modern note paper, covered with an endless array of figures in even lines, written small and with exquisite care. The paper was just such a size as might be put as marker in an ordinary quarto; that it had been so used was manifest by the discolouration of a portion of it that had evidently stuck out at the top of the volume. Fortunately, in its long dusty rest in the bookshelf the side written on had been downward so that the figures, though obscured by dust and faded by light and exposure to the air, were still decipherable. This paper I examined most carefully with a microscope; but could see in it no signs of secret writing beyond what might be contained in the disposition of the numbers themselves. I got a sheet of foolscap and made an enlarged copy, taking care to leave fair space between the rows of figures and between the figures themselves.
Then I placed the copy of figures and the first of the dotted pages side by side before me and began to study them.
I confined my attention at first chiefly to the paper of figures, for it struck me that it would of necessity be the simpler of the two systems to read, inasmuch as the symbols should be self-contained. In the dotted letters it was possible that more than one element existed, for the disposition of significants appeared to be of endless variety, and the very novelty of the method—it being one to which the eyes and the senses were not accustomed—made it a difficult one to follow at first. I had little doubt, however, that I should ultimately find the dot cipher the more simple of the two, when I should have learned its secret and become accustomed to its form. Its mere bulk made the supposition likely that it was in reality simple; for it would be indeed an endless task, to work out in this laborious form two whole sheets of a complicated cipher.
Over and over and over again I read the script of numbers. Forward and backward; vertically; up and down, for the lines both horizontal and vertical were complete and exact, I read it. But nothing struck me of sufficient importance to commence with as a beginning.
Of course there were here and there repetitions of the same combination of figures, sometimes two, sometimes three, sometimes four together; but of the larger combinations the instances were rare and did not afford me any suggestion of a clue!
So I became practical, and spent the remainder of my work-time that day in making by aid of my microscope an exact but enlarged copy, but in Roman letters, of the first of the printed pages.