But I did not at the time give this much thought. I was interested in pushing deeper into that tunnel, and I did so, going as far in the direction, I thought, of the seacoast, as I could before my passage was blocked by a fall of earth. When at last I left the tunnel it was late in the afternoon, and I was famished; but I was reasonably certain of two things—the tunnel was not a natural cave, at least at this end; it was clearly the work of human hands; and it had been used for some dark purpose, the nature of which I could not know.