She could hardly go wrong either as to the passage at the top of it, leading back over the room she had just left below, but she could not tell which was her own door.

Fearing to open the wrong one, she passed it and went on to the end of the corridor, which was very dimly lighted.

There she came to an open door, through which she saw a small chamber, evidently not meant for habitation.

She entered.

A little light came in through a crossed loophole, sufficient to show her the bare walls, with the plaster sticking out between the stones, the huge beams above, and in the middle of the floor, opposite the loop-hole, a great arblast or cross-bow, with its strange machinery.