At the end of the passage a door was walled up. It led, in the times of the republic, to dungeons under the canal, in which the prisoner died in eight days from his incarceration, at the farthest, from the noisome dampness and unwholesome vapors of the place. The guide gave us a harrowing description of the swelling of their bodies, and the various agonies of their slow death. I hurried away from the place with a sickness at my heart. In returning by the same way I passed the turning, and stumbled over a raised stone across the passage. It was the groove of a secret guillotine. Here many of the state and inquisition victims were put to death in the darkness of a narrow passage, shut out even in their last moment from the light and breath of heaven. The frame of the instrument had been taken away; but the pits in the wall, which had sustained the axe, were still there; and the sink on the other side, where the head fell, to carry off the blood. And these shocking executions took place directly before the cells of the other prisoners, within twenty feet from the farthest. In a cell close to this guillotine had been confined a state criminal for sixteen years. He was released at last by the arrival of the French, and on coming to the light in the square of San Marc was struck blind, and died in a few days. In another cell we stopped to look at the attempts of a prisoner upon its walls, interrupted, happily, by his release. He had sawed several inches into the front wall, with some miserable instrument, probably a nail. He had afterward abandoned this, and had, with prodigious strength, taken up a block from the floor; and, the guide assured us, had descended into the cell below. It was curious to look around his pent prison, and see the patient labor of years upon those rough walls, and imagine the workings of the human mind in such a miserable lapse of existence. We ascended to the light again, and the guide led us to a massive door, with two locks, secured by heavy iron bars. It swung open with a scream, and we mounted a winding stair, and "Stood in Venice on the Bridge of Sighs."