“The meaning of the thing was so very plain,” Hewitt said to me afterwards, “that the duffers who had the ‘Flitterbat Lancers’ in hand for so long never saw it at all. If Shiels had made an ordinary clumsy cryptogram, all letters and figures, they would have seen what it was at once, and at least would have tried to read it; but because it was put in the form of music, they tried everything else but the right way. It was a clever dodge of Shiels’s, without a doubt. Very few people, police officers or not, turning over a heap of old music, would notice or feel suspicious of that little slip among the rest. But once one sees it is a cryptogram (and the absence of bar-lines and of notes beyond the stave would suggest that) the reading is as easy as possible. For my part I tried it as a cryptogram at once. You know the plan--it has been described a hundred times. See here--look at this copy of the ‘Flitterbat Lancers.’ Its only difficulty--and that is a small one--is that the words are not divided. Since there are on the stave positions for less than a dozen notes, and there are twenty-six letters to be indicated, it follows that crotchets, quavers, and semiquavers on the same line or space must mean different letters. The first step is obvious. We count the notes to ascertain which sign occurs most frequently, and we find that the crotchet in the top space is the sign required--it occurs no less than eleven times. Now the letter most frequently occurring in an ordinary sentence of English is _e_. Let us then suppose that this represents _e_. At once a coincidence strikes us. In ordinary musical notation in the treble clef the note occupying the top space would be E. Let us remember that presently. Now the most common word in the English language is _the_. We know the sign for _e_, the last letter of this word, so let us see if in more than one place that sign is preceded by two others identical in each case. If so, the probability is that the other two signs will represent _t_ and _h_, and the whole word will be _the_. Now it happens in no less than four places the sign _e_ is preceded by the same two other signs--once in the first line, twice in the second, and once in the fourth. No word of three letters ending in _e_ would be in the least likely to occur four times in a short sentence except _the_. Then we will call it _the_, and note the signs preceding the _e_. They are a quaver under the bottom line for the _t_, and a crotchet on the first space for the _h_. We travel along the stave, and wherever these signs occur we mark them with _t_ or _h_, as the case may be. But now we remember that _e_, the crotchet in the top space, is in its right place as a musical note, while the crotchet in the bottom space means _h_, which is no musical note at all. Considering this for a minute, we remember that among the notes which are expressed in ordinary music on the treble stave, without the use of ledger lines, _d e_ and _f_ are