In fact, the level continued to rise gradually. There were then six feet of water inside the cone. 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. Besides, to wait longer was not possible. Asphyxia was threatening in this narrow space, reduced every moment, in a medium already saturated with carbonic acid.

The best tool Dick Sand could employ to pierce a hole through the wall was a ramrod furnished with a screw, intended to draw the wadding from a gun. By making it turn rapidly, this screw scooped out the clay like an auger, and the hole was made little by little. Then it would not have a larger diameter than that of the ramrod, but that would be sufficient. The air could come through very well.

Hercules holding up the lantern lighted Dick Sand. They had some wax candles to take its place, and they had not to fear lack of light from that source.

A minute after the beginning of the operation, the ramrod went freely through the wall. At once a rather dull noise was produced, resembling that made by globules of air escaping through a column of water. The air escaped, and, at the same moment, the level of the water rose in the cone, and stopped at the height of the hole. This proved that they had pierced too low--that is to say, below the liquid mass.

"Begin again," the young novice said, coolly, after rapidly stopping the hole with a handful of clay.

The water was again stationary in the cone, but the reserved space had diminished more than eight inches. Respiration became difficult, for the oxygen was beginning to fail. They saw it also by the lantern's light, which reddened and lost a part of its brightness.

One foot above the first hole, Dick Sand began at once to pierce a second by the same process. If the experiment failed, the water would rise still higher inside the cone--but that risk must be run.

While Dick Sand was working his auger, they heard Cousin Benedict cry out, suddenly:

"Mercy! look--look--look why!"

Hercules raised his lantern and threw its light on Cousin Benedict, whose face expressed the most perfect satisfaction.

"Yes," repeated he, "look why those intelligent termites have abandoned the ant-hill! They had felt the inundation beforehand. Ah! instinct, my friends, instinct. The termites are wiser than we are, much wiser."

And that was all the moral Cousin Benedict drew from the situation.

At that moment Dick Sand drew out the ramrod, which had penetrated the wall. A hissing was produced. The water rose another foot inside the cone--the hole had not reached the open air outside.

The situation was dreadful. Mrs. Weldon, then almost reached by the water, had raised little Jack in her arms. All were stifling in this narrow space. Their ears buzzed.

The lantern only threw a faint light.

"Is the cone, then, entirely under water?" murmured Dick Sand.

He must know; and, in order to know, he must pierce a third hole, at the very top.