"Sometimes that is the case. Many of these woods have become true anthracites, but others again, like those you see before you, have only undergone one phase of fossil transformation. But there is no proof like demonstration," added my uncle, picking one or two of these precious waifs and casting them into the sea. The piece of wood, after having disappeared for a moment, came to the surface, and floated about with the oscillation produced by wind and tide. "Are you convinced?" said my uncle, with a self-satisfied smile. "I am convinced," I cried, "that what I see is incredible." The fact was that my journey into the interior of the earth was rapidly changing all preconceived notions, and day by day preparing me for the marvelous. I should not have been surprised to have seen a fleet of native canoes afloat upon that silent sea. The very next evening, thanks to the industry and ability of Hans, the raft was finished. It was about ten feet long and five feet wide. The beams bound together with stout ropes, were solid and firm, and once launched by our united efforts, the improvised vessel floated tranquilly upon the waters of what the Professor had well named the Central Sea. CHAPTER 29 ON THE WATERS--A RAFT VOYAGE On the thirteenth of August we were up betimes. There was no time to be lost. We now had to inaugurate a new kind of locomotion, which would have the advantage of being rapid and not fatiguing. A mast, made of two pieces of wood fastened together, to give additional strength, a yard made from another one, the sail a linen sheet from our bed. We were fortunately in no want of cordage, and the whole on trial appeared solid and seaworthy. At six o'clock in the morning, when the eager and enthusiastic Professor gave the signal to embark, the victuals, the luggage, all our instruments, our weapons, and a goodly supply of sweet water, which we had collected from springs in the rocks, were placed on the raft. Hans had, with considerable ingenuity, contrived a rudder, which enabled him to guide the floating apparatus with ease. He took the tiller, as a matter of course. The worthy man was as good a sailor as he was a guide and duck hunter. I then let go the painter which held us to the shore, the sail was brought to the wind, and we made a rapid offing. Our sea voyage had at length commenced; and once more we were making for distant and unknown regions. Just as we were about to leave the little port where the raft had been constructed, my uncle, who was very strong as to geographic nomenclature, wanted to give it a name, and among others, suggested mine. "Well," said I, "before you decide I have another to propose." "Well; out with it." "I should like to call it Gretchen. Port Gretchen will sound very well on our future map." "Well then, Port Gretchen let it be," said the Professor. And thus it was that the memory of my dear girl was attached to our adventurous and memorable expedition.