"Let us advance, then," I cried eagerly, no longer able to restrain my curiosity.

"Wait a moment, my dear Harry," he responded; "you must take precautions after your illness before going into the open air."

"The open air?"

"Yes, my boy. I have to warn you that the wind is rather violent—and I have no wish for you to expose yourself without necessary precautions."

"But I beg to assure you that I am perfectly recovered from my illness."

"Have just a little patience, my boy. A relapse would be inconvenient to all parties. We have no time to lose—as our approaching sea voyage may be of long duration."

"Sea voyage?" I cried, more bewildered than ever.

"Yes. You must take another day's rest, and we shall be ready to go on board by tomorrow," replied my uncle, with a peculiar smile.

"Go on board!" The words utterly astonished me.

Go on board—what and how? Had we come upon a river, a lake, had we discovered some inland sea? Was a vessel lying at anchor in some part of the interior of the earth?