I took a pencil and a spare sheet of paper, and I studied those figures all through lunch and for some little time after. It soon became plain that the problem was much more difficult than it looked, and I said so. "At the first glance," I said, "it looked a fairly easy cypher; but as a matter of fact, I don't think it's easy at all. One assumes, of course, that the figures stand for letters, and on that assumption two or three peculiarities are noticeable. First, the highest number written here is 23, so that all the letters indicated, in whatever order they may come, are within the compass of the twenty-six letters of the alphabet. Next, the numbers most frequently repeated, if we except the noughts, are 5 and 20, which occur seven times each. Now, the vowel most frequently occurring in average English writing is e, and you will at once perceive that e is number five in the alphabet, counting from the beginning. More, if we go on counting so, we shall find that 20 is _t_, which is one of the most frequently occurring consonants. This would seem to hint that the cypher is of the very simplest description, consisting of the mere substitution of figures for letters in the exact order of the alphabet. But what, then, of the noughts? What can they mean? More especially when we consider that in three places there are actually four noughts in succession; for, of course, no letter is repeated four times successively in any English word, nor in any foreign word that I can imagine. But let us put down the letters in substitution for the figures, on the supposition that the figures stand for letters in their alphabetical order, leaving the noughts as they are. Then we get this." I rapidly pencilled the letters on the spare paper, thus:--_i, h, n, d, t, r, e, i; o, s, t, 0, c, i, h, e; c, w, 0, 0, e, m, n, s; s, t, 0, 0, 0, 0, f, a; e, t, 0, 0, 0, 0, c, v; a, o, 0, 0, 0, 0, r, e; a, h, t, k, r, i, e, t; l, e, w, n, n, a, a, t_.