"Twist these first and last letters into the position indicated by the cipher. Then we shall see what will happen." I put forth my strength to the "A," and found that with an effort it twisted with considerable ease. "Hurrah!" I cried, "this is the secret." The final "S" was more difficult to move, but at last I contrived to get it twisted completely round. Gertrude's bright face looked up anxiously. "Stand away; stand away," I cried hastily. It was just as well that I had warned her, for suddenly the whole broad board containing the motto clattered to the floor before I could save it. "The diamonds! the diamonds!" cried Gertrude excitedly. A cavity was revealed, and I passed my hand along. It was empty. "Gertrude, the diamonds are gone!" I cried in dismay, and our spirits fell to zero. CHAPTER XXI. THE AIRSHIP Who had removed the diamonds? That was my thought for the next twenty-four hours, but I could not answer my own question. I certainly remembered how Striver insisted that Mr. Monk had secured possession of the fortune. But only by getting possession of the eye could he learn where the jewels were hidden; and by Striver's own showing he had not been thus fortunate. Only when destroying the eye had he had it in his hands, and then, instead of reading the cipher, he had thrown the coin upon which it was written into the Thames. Moreover, for many months Monk had been masquerading as Wentworth Marr, and had possessed the money to keep up the farce. Undoubtedly--as I thought, after much reflection--the story of Australian legacy must be true. Mr. Monk, on the face of it, could not have looted the beam of its valuable contents. But what astonished me was that Monk should have thrown away the coin, although it was natural enough that he should have destroyed the eye. But why did he not at least attempt to read the cipher? It seemed to be an extremely easy one, as the repetition of the beam's carving on the coin suggested the Latin motto. The reversed letters suggested a little hard thinking, but presented no great obstacle. The late Gabriel Monk had cut away the inscribed board, and behind had hollowed out a place for the reception of the diamonds--in a bag, I presume. Also he had cut out the first and last letters of the saying in circular form, and to these had attached pieces of iron. When the letters were placed straightly these pieces of iron caught on to the inner part of the beam, and so held the inscribed board; when reversed, they released the same. It was ingenious but not difficult of solution, and I wondered that Monk had not read the cipher. If he had, he certainly would have guessed that the beam in The Lodge smoking-room held the jewels, and in that event would have searched. On this assumption I thought that the man could not have examined the cipher. But why he should not have done so puzzled me considerably.