Of this Rupert took hold, and remained quiescent as the water mounted higher and higher; presently it rose above the top of the loophole, and Rupert now watched anxiously how fast it ran.

Floating on his back, and keeping a finger at the water level against the wall, he could feel that the water still rose.

It seemed to him that the rise was slower and slower, and at last his finger remained against a point in the stones for some minutes without moving.

The rise of the water inside the dungeon had ceased.
That it continued outside he guessed by a slight but distinct feeling of pressure in the air, showing that the column of water outside was compressing it.

He had no fear of any bad consequences from this source, as even a height of twelve feet of water outside would not give any unbearable pressure.