It was about eight o'clock when they commenced their difficult ascent; the sky was splendid, and the thermometer stood at 52°.
Hatteras and his dog went first, closely followed by the others.
"I am afraid," said Johnson to the Doctor.
"No, no, there's nothing to be afraid of; we are here."
This singular little island appeared to be of recent formation, and was evidently the product of successive volcanic eruptions. The rocks were all lying loose on the top of each other, and it was a marvel how they preserved their equilibrium. Strictly speaking, the mountain was only a heap of stones thrown down from a height, and the mass of rocks which composed the island had evidently come out of the bowels of the earth.
The earth, indeed, may be compared to a vast cauldron of spherical form, in which, under the influence of a central fire, immense quantities of vapours are generated, which would explode the globe but for the safety-valves outside.
These safety-valves are volcanoes, when one closes another opens; and at the Poles where the crust of the earth is thinner, owing to its being flattened, it is not surprising that a volcano should be suddenly formed by the upheaving of some part of the ocean-bed.
The Doctor, while following Hatteras, was closely following all the peculiarities of the island, and he was further confirmed in his opinion as to its recent formation by the absence of water. Had it existed for centuries, the thermal springs would have flowed from its bosom.
As they got higher, the ascent became more and more difficult, for the flanks of the mountain were almost perpendicular, and it required the utmost care to keep them from falling. Clouds of scoriæ and ashes would whirl round them repeatedly, threatening them with asphyxia, or torrents of lava would bar their passage. In parts where these torrents ran horizontally, the outside had become hardened; while underneath was the boiling lava, and every step the travellers took had first to be tested with the iron-tipped staff to avoid being suddenly plunged into the scalding liquid.
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.