"What depth have we now reached?"

"We are thirty-five leagues below the surface."

"So," I said, examining the map, "the Highlands of Scotland are over our heads, and the Grampians are raising their rugged summits above us."

"Yes," answered the Professor laughing. "It is rather a heavy weight to bear, but a solid arch spans over our heads. The great Architect has built it of the best materials; and never could man have given it so wide a stretch. What are the finest arches of bridges and the arcades of cathedrals, compared with this far reaching vault, with a radius of three leagues, beneath which a wide and tempest-tossed ocean may flow at its ease?"

"Oh, I am not afraid that it will fall down upon my head. But now what are your plans? Are you not thinking of returning to the surface now?"

"Return! no, indeed! We will continue our journey, everything having gone on well so far."

"But how are we to get down below this liquid surface?"

"Oh, I am not going to dive head foremost. But if all oceans are properly speaking but lakes, since they are encompassed by land, of course this internal sea will be surrounded by a coast of granite, and on the opposite shores we shall find fresh passages opening."

"How long do you suppose this sea to be?"

"Thirty or forty leagues; so that we have no time to lose, and we shall set sail to-morrow."

I looked about for a ship.

"Set sail, shall we? But I should like to see my boat first."

"It will not be a boat at all, but a good, well-made raft."

"Why," I said, "a raft would be just as hard to make as a boat, and I don't see--"

"I know you don't see; but you might hear if you would listen. Don't you hear the hammer at work? Hans is already busy at it."

"What, has he already felled the trees?"

"Oh, the trees were already down. Come, and you will see for yourself."

After half an hour's walking, on the other side of the promontory which formed the little natural harbour, I perceived Hans at work. In a few more steps I was at his side. To my great surprise a half-finished raft was already lying on the sand, made of a peculiar kind of wood, and a great number of planks, straight and bent, and of frames, were covering the ground, enough almost for a little fleet.

"Uncle, what wood is this?" I cried.

"It is fir, pine, or birch, and other northern coniferae, mineralised by the action of the sea. It is called surturbrand, a variety of brown coal or lignite, found chiefly in Iceland."

"But surely, then, like other fossil wood, it must be as hard as stone, and cannot float?"

"Sometimes that may happen; some of these woods become true anthracites; but others, such as this, have only gone through the first stage of fossil transformation. Just look," added my uncle, throwing into the sea one of those precious waifs.

The bit of wood, after disappearing, returned to the surface and oscillated to and fro with the waves.

"Are you convinced?" said my uncle.

"I am quite convinced, although it is incredible!"

By next evening, thanks to the industry and skill of our guide, the raft was made. It was ten feet by five; the planks of surturbrand, braced strongly together with cords, presented an even surface, and when launched this improvised vessel floated easily upon the waves of the Liedenbrock Sea.