Dick Sand saw that all was well. No immediate danger seemed to menace these human termites, substituted for the colony of newroptera. The young novice then thought of refreshing himself by a few hours' sleep, as he already felt its influence. Only with supreme precaution Dick Sand lay on that bed of clay, at the bottom of the cone, near the narrow edifice.

By this means, if any accident happened outside, he would be the first to remark it. The rising day would also awaken him, and he would be ready to begin the exploration of the plain.

Dick Sand lay down then, his head against the wall, his gun under his hand, and almost immediately he was asleep.

How long this drowsiness lasted he could not tell, when he was awakened by a lively sensation of coolness.

He rose and recognized, not without great anxiety, that the water was invading the ant hill, and even so rapidly, that in a few seconds it would reach the story of cells occupied by Tom and Hercules.

The latter, awakened by Dick Sand, were told about this new complication.

The lighted lantern soon showed the interior of the cone.

The water had stopped at a height of about five feet, and remained stationary.

"What is the matter, Dick?" asked Mrs. Weldon.

"It is nothing," replied the young novice. "The lower part of the cone has been inundated. It is probably that during this storm a neighboring river has overflowed on this plain."

"Good!" said Hercules; "that proves the river is there!"

"Yes," replied Dick Sand, "and it will carry us to the coast. Be reassured, then, Mrs. Weldon; the water cannot reach you, nor little Jack, nor Nan, nor Mr. Benedict."

Mrs. Weldon did not reply. As to the cousin, he slept like a veritable termite.

Meanwhile the blacks, leaning over this sheet of water, which reflected the lantern's light, waited for Dick Sand to indicate to them what should be done. He was measuring the height of the inundation.

After having the provisions and arms put out of the reach of the inundation, Dick Sand was silent.

"The water has penetrated by the orifice," said Tom.

"Yes," replied Dick Sand, "and now it prevents the interior air from being renewed."

"Could we not make a hole in the wall above the level of the water?" asked the old black.

"Doubtless, Tom; but if we have five feet of water within, there are perhaps six or seven, even more, without."

"You think, Mr. Dick--?"

"I think, Tom, that the water, rising inside the ant-hill, has compressed the air in the upper part, and that this air now makes an obstacle to prevent the water from rising higher. But if we pierce a hole in the wall by which the air would escape, either the water would still rise till it reached the outside level, or if it passed the hole, it would rise to that point where the compressed air would again keep it back. We must be here like workmen in a diving-bell."

"What must be done?" asked Tom.

"Reflect well before acting," replied Dick Sand. "An imprudence might cost us our lives!"

The young novice's observation was very true.

In comparing the cone to a submerged bell, he was right. Only in that apparatus the air is constantly renewed by means of pumps. The divers breathe comfortably, and they suffer no other inconveniences than those resulting from a prolonged sojourn in a compressed atmosphere, no longer at a normal pressure.

But here, beside those inconveniences, space was already reduced a third by the invasion of the water. As to the air, it would only be renewed if they put it in communication with the outer atmosphere by means of a hole.

Could they, without running the danger spoken of by Dick Sand, pierce that hole? Would not the situation be aggravated by it?

What was certain was, that the water now rested at a level which only two causes could make it exceed, namely: if they pierced a hole, and the level of the rising waters was higher outside, or if the height of this rising water should still increase. In either of these cases, only a narrow space would remain inside the cone, where the air, not renewed, would be still more compressed.