Down below him Matt could hear Dick roaring his order to Clackett. With eyes against one of the narrow windows Matt watched the rebel soldiers.
They were beating on the hatch cover with their fists, and kicking against the sides of the tower. On the bank, their comrades were running along to keep abreast of the boat and shouting suggestions.
The Grampus, steered by Dick with the aid of the periscope, had turned her nose down-stream in the direction of the Izaral.
The hissing of air escaping from the ballast tanks as the water came in was heard by the four ragamuffins on the outside of the steel shell.
From their actions, they began to feel alarm. This strange craft was more than their primitive minds could comprehend.
Slowly the submarine began to sink. As the water crept up the rounded deck, the negroes lifted their bare feet out of it gingerly and pushed up higher. One of them leaped onto the conning-tower hatch.
Then, suddenly, the Grampus dropped below the water. A mud-colored blur closed Matt's view through the lunette, and as he slid down the ladder into the periscope room, he heard faint yells from the negroes.
Dick, hanging over the periscope table, twirling the steering wheel, was laughing loudly.
"Look, Matt!" he cried. "If you ever saw a lot of scared Sambos, there they are, up there in the Purgatoire!"
Matt stepped to Dick's side and peered down upon the mirror. Far behind, in the trail of bubbles sent up from the Grampus, the four negroes were swimming like mad toward the shore. Their comrades on the bank were leaning out to help them, and it was evident that they would all be saved.