By degrees the passage narrowed, yet the duke continued his course.

It was a dangerous undertaking; for he would be trapped if the passage narrowed.

The passage narrowed and curved sharply three or four times.

Here the passage narrowed, and the ceiling became lower.

The passage narrowed to the extent that they had to squeeze through it single file.

The passage narrowed to three feet in width, but the roof stayed out of reach above his head.

Shortly after they passed the hole, the passage narrowed again into something even smaller than before.

The passage narrowed some more until it was no more than ten feet wide.

Ahead, past the debris, the passage narrowed even more to about the width of an average doorway.

The deep passage narrowed and curved off to the left about a quarter of a mile north.