At that time the heat had become overwhelming.  It would even have been unbearable, if thick storm clouds had not interposed between the burning rays and the ground.  Distant lightnings began to rend the sky and low rollings of thunder grumbled in the depths of the heavens.  A formidable storm was going to burst forth.

Now, these cataclysms are terrible in Africa:  rain in torrents, squalls of wind which the strongest trees cannot resist, clap after clap of thunder, such is the contest of the elements in that latitude.

Dick Sand knew it well, and he became very uneasy.  They could not pass the night without shelter.  The plain was likely to be inundated, and it did not present a single elevation on which it was possible to seek refuge.

But refuge, where would they seek it in this low desert, without a tree, without a bush?  The bowels of the earth even would not give it.  Two feet below the surface they would find water.

However, toward the north a series of low hills seemed to limit the marshy plain.  It was as the border of this depression of land.  A few trees were profiled there on a more distant, clearer belt, left by the clouds on the line of the horizon.

There, if shelter were still lacking, the little band would at least no longer risk being caught in a possible inundation.  There perhaps was salvation for all.

“Forward, my friends, forward!” repeated Dick Sand.  “Three miles more and we shall be safer than in these bottom-lands.”

“Hurry! hurry!” cried Hercules.

The brave black would have wished to take that whole world in big arms and carry it alone.

Those words inspired those courageous men, and in spite of the fatigue of a day’s march, they advanced more quickly than they had done at the commencement from the halting-place.

When the storm burst forth the end to be attained was still more than two miles off.  Now—­a fact which was the more to be feared—­the rain did not accompany the first lightnings exchanged between the ground and the electrical clouds.  Darkness then became almost complete, though the sun had not disappeared below the horizon.  But the dome of vapors gradually lowered, as if it threatened to fall in—­a falling in which must result in a torrent of rain.  Lightnings, red or blue, split it in a thousand places, and enveloped the plain in an inextricable network of fire.

Twenty times Dick and his companions ran the risk of being struck by lightning.  On this plateau, deprived of trees, they formed the only projecting points which could attract the electrical discharges.  Jack, awakened by the noise of the thunder, hid himself in Hercules’ arms.  He was very much afraid, poor little boy, but he did not wish to let his mother see it, for fear of afflicting her more.  Hercules, while taking great steps, consoled him as well as he could.

“Do not be afraid, little Jack,” he repeated.  “If the thunder comes near us, I will break it in two with a single hand.  I am stronger than it!”