it seemed at first insuperable.  I tore a part of the hem from the robe and placed the fragment at full length, and at right angles to the wall.  In groping my way around the prison, I could not fail to encounter this rag upon completing the circuit.  So, at least I thought:  but I had not counted upon the extent of the dungeon, or upon my own weakness.  The ground was moist and slippery.  I staggered onward for some time, when I stumbled and fell.  My excessive fatigue induced me to remain prostrate; and sleep soon overtook me as I lay.

Upon awaking, and stretching forth an arm, I found beside me a loaf and a pitcher with water.  I was too much exhausted to reflect upon this circumstance, but ate and drank with avidity.  Shortly afterward, I resumed my tour around the prison, and with much toil came at last upon the fragment of the serge.  Up to the period when I fell I had counted fifty-two paces, and upon resuming my walk, I had counted forty-eight more; —­ when I arrived at the rag.  There were in all, then, a hundred paces; and, admitting two paces to the yard, I presumed the dungeon to be fifty yards in circuit.  I had met, however, with many angles in the wall, and thus I could form no guess at the shape of the vault; for vault I could not help supposing it to be.

I had little object —­ certainly no hope these researches; but a vague curiosity prompted me to continue them.  Quitting the wall, I resolved to cross the area of the enclosure.  At first I proceeded with extreme caution, for the floor, although seemingly of solid material, was treacherous with slime.  At length, however, I took courage, and did not hesitate to step firmly; endeavoring to cross in as direct a line as possible.  I had advanced some ten or twelve paces in this manner, when the remnant of the torn hem of my robe became entangled between my legs.  I stepped on it, and fell violently on my face.

In the confusion attending my fall, I did not immediately apprehend a somewhat startling circumstance, which yet, in a few seconds afterward, and while I still lay prostrate, arrested my attention.  It was this —­ my chin rested upon the floor of the prison, but my lips and the upper portion of my head, although seemingly at a less elevation than the chin, touched nothing.  At the same time my forehead seemed bathed in a clammy vapor, and the peculiar smell of decayed fungus arose to my nostrils.  I put forward my arm, and shuddered to find that I had fallen at the very brink of a circular pit, whose extent, of course, I had no means of ascertaining at the moment.  Groping about the masonry just below the margin, I succeeded in dislodging a small fragment, and let it fall into the abyss.  For many seconds I hearkened to its reverberations as it dashed against the sides of the chasm in its descent; at length there was a sullen plunge into water, succeeded by loud echoes.  At the same moment there came a sound resembling the quick opening, and as rapid closing of a door overhead, while a faint gleam of light flashed suddenly through the gloom, and as suddenly faded away.