After a night's sweet repose, we awoke fresh and ready for action. There being nothing to detain us, we started on our journey. We continued to burrow through the lava tunnel as before. It was impossible to make out through what soil we were making way. The tunnel, moreover, instead of going down into the bowels of the earth, became absolutely horizontal.
I even thought, after some examination, that we were actually tending upwards. About ten o'clock in the day this state of things became so clear that, finding the change very fatiguing, I was obliged to slacken my pace and finally come to a halt.
"Well," said the Professor quickly, "what is the matter?"
"The fact is, I am dreadfully tired," was my earnest reply.
"What," cried my uncle, "tired after a three hours' walk, and by so easy a road?"
"Easy enough, I dare say, but very fatiguing."
"But how can that be, when all we have to do is to go downwards."
"I beg your pardon, sir. For some time I have noticed that we are going upwards."
"Upwards," cried my uncle, shrugging his shoulders, "how can that be?"
"There can be no doubt about it. For the last half hour the slopes have been upward—and if we go on in this way much longer we shall find ourselves back in Iceland."