With the exception of Mrs.Weldon, her son, Cousin Benedict, and Nan, who had taken refuge in the upper cavities, all were immersed to the waist.
Then there was a necessity for quick action, as Dick Sand proposed.
It was one foot above the interior level, consequently seven feet from the ground, that Dick Sand resolved to pierce a hole in the clay wall.
If, by this hole, they were in communication with the outer air, the cone emerges.

If, on the contrary, this hole was pierced below the water level outside, the air would be driven inward, and in that case they must stop it up at once, or the water would rise to its orifice.
Then they would commence again a foot higher, and so on.

If, at last, at the top, they did not yet find the outer air, it was because there was a depth of more than fifteen feet of water in the plain, and that the whole termite village had disappeared under the inundation.

Then what chance had the prisoners in the ant-hill to escape the most terrible of deaths, death by slow asphyxia?
Dick Sand knew all that, but he did not lose his presence of mind for a moment.

He had closely calculated the consequences of the experiment he wished to try.