"I don't think a phonograph would show any record of that. The sound doesn't come to me by the ears at all. The vibrations reach me in another manner altogether, and seem to be within me, which is precisely how a fourth dimension sound might be supposed to make itself heard." I purposely made no reply to this, but I sat up a little closer to the fire and peered about me into the darkness. The clouds were massed all over the sky and no trace of moonlight came through. Very still, too, everything was, so that the river and the frogs had things all their own way. "It has that about it," he went on, "which is utterly out of common experience. It is _unknown_. Only one thing describes it really: it is a non-human sound; I mean a sound outside humanity." Having rid himself of this indigestible morsel, he lay quiet for a time; but he had so admirably expressed my own feeling that it was a relief to have the thought out, and to have confined it by the limitation of words from dangerous wandering to and fro in the mind. The solitude of that Danube camping-place, can I ever forget it? The feeling of being utterly alone on an empty planet! My thoughts ran incessantly upon cities and the haunts of men. I would have given my soul, as the saying is, for the "feel" of those Bavarian villages we had passed through by the score; for the normal, human commonplaces, peasants drinking beer, tables beneath the trees, hot sunshine, and a ruined castle on the rocks behind the red-roofed church. Even the tourists would have been welcome. Yet what I felt of dread was no ordinary ghostly fear. It was infinitely greater, stranger, and seemed to arise from some dim ancestral sense of terror more profoundly disturbing than anything I had known or dreamed of. We had "strayed," as the Swede put it, into some region or some set of conditions where the risks were great, yet unintelligible to us; where the frontiers of some unknown world lay close about us. It was a spot held by the dwellers in some outer space, a sort of peephole whence they could spy upon the earth, themselves unseen, a point where the veil between had worn a little thin. As the final result of too long a sojourn here, we should be carried over the border and deprived of what we called "our lives," yet by mental, not physical, processes. In that sense, as he said, we should be the victims of our adventure--a sacrifice.