At intervals large fragments of red-hot rock were thrown up from the crater, and burst in the air like bomb-shells, scattering the debris to enormous distances in all directions.

Hatteras, however, climbed up the steepest ascents with surprising agility, disdaining the help of his staff.

He arrived before long at a circular rock, a sort of plateau about ten feet wide. A river of boiling lava surrounded it, except in one part, where it forked away to a higher rock, leaving a narrow passage, through which Hatteras fearlessly passed.

Here he stopped, and his companions managed to rejoin him. He seemed to be measuring with his eye the distance he had yet to get over. Horizontally, he was not more than two hundred yards from the top of the crater, but vertically he had nearly three times that distance to traverse.

The ascent had occupied three hours already. Hatteras showed no signs of fatigue, while the others were almost spent.

The summit of the volcano appeared inaccessible, and the Doctor determined at any price to prevent Hatteras from attempting to proceed. He tried gentle means first, but the captain's excitement was fast becoming delirium. During their ascent, symptoms of insanity had become more and more marked, and no one could be surprised who knew anything of his previous history.

"Hatteras," said the Doctor, "it is enough! we cannot go further!"

"Stop, then," he replied, in a strangely altered voice; "I am going higher."

"No, it is useless; you are at the Pole already."

"No, no! higher, higher!"

"My friend, do you know who is speaking to you? It is I, Doctor Clawbonny."

"Higher, higher!" repeated the madman.

"Very well, we shall not allow it-that is all."

He had hardly uttered the words before Hatteras, by a superhuman effort, sprang over the boiling lava, and was beyond the reach of his companions.

A cry of horror burst from every lip, for they thought the poor captain must have perished in that fiery gulf; but there he was safe on the other side, accompanied by his faithful Duk, who would not leave him.

He speedily disappeared behind a curtain of smoke, and they heard his voice growing fainter in the distance, shouting-

"To the north! to the north! to the top of Mount Hatteras! Remember Mount Hatteras!"

All pursuit of him was out of the question; it was impossible to leap across the fiery torrent, and equally impossible to get round it. Altamont, indeed, was mad enough to make an attempt, and would certainly have lost his life if the others had not held him back by main force.

"Hatteras! Hatteras!" shouted the Doctor, but no response was heard save the faint bark of Duk.

At intervals, however, a glimpse of him could be caught through the clouds of smoke and showers of ashes. Sometimes his head, sometimes his arm appeared; then he was out of sight again, and a few minutes later was seen higher up clinging to the rocks. His size constantly decreased with the fantastic rapidity of objects rising upwards in the air. In half-an-hour he was only half his size.

The air was full of the deep rumbling noise of the volcano, and the mountain shook and trembled. From time to time a loud fail was heard behind, and the travellers would see some enormous rock rebounding from the heights to engulph itself in the polar basin below.

[Illustration: Hatteras did not even turn once to look back, but marched straight on, carrying his country's flag attached to his staff.-P.249]

Hatteras did not even turn once to look back, but marched straight on, carrying his country's flag attached to his staff. His terrified friends watched every movement, and saw him gradually decrease to microscopic dimensions, while Duk looked no larger than a big rat.

Then came a moment of intense anxiety, for the wind beat down on them an immense sheet of flame, and they could see nothing but the red glare. A cry of agony escaped the Doctor; but an instant afterwards Hatteras reappeared, waving his flag.

For a whole hour this fearful spectacle went on-an hour of battle with unsteady loose rocks and quagmires of ashes, where the foolhardy climber sank up to his waist.