[Footnote 8: "Considering that the mean density of the whole earth is only about five and a half times that of water, and that the materials of which the crust of the earth is composed are all compressible in a greater or less degree, so that even at no very great depth the density of the different substances must be greatly increased by the mere pressure of the superincumbent materials, some philosophers have supposed that the effects of pressure must be counterbalanced by the expansive force of a great heat subsisting in the interior of the earth; and others that the earth is not solid, _but merely a hollow shell_ of inconsiderable thickness."--Brande.] The age of our angel, by the way, I placed at about twenty-five years. And I wondered how they could possibly reckon time here in this underground world, a world that could have neither days nor months nor years. The quartette listened eagerly to the explanations given by our angel. Suddenly the leader addressed some question to Persephone, as Rhodes called her. And then we heard it! "Drome," was her answer. There it was, distinct, unmistakable, that mysterious word which had given us so many strange and wild thoughts and visions. Yes, there it was; and it was an answer, I thought, that by no means put the man's mind at ease. Drome! Drome at last. But--but what did it mean? Drome! There, we distinctly heard the angel pronounce the word again. Drome! If we could only have understood the words being spoken! But there was no mistaking, I thought, the manner of the angel. It was earnest, and yet, strangely enough, that Sibylline quality about her was now more pronounced than ever. But there was no mistaking her manner: she was endeavoring to reassure him, then, to allay, it seemed, some strange uneasiness or fear. I noticed, however, with some vague, sinister misgivings, that in this she was by no means as successful as she herself desired. Why did we see in the eyes of the leader, and in those of the others, so strange, so mysterious a look whenever those eyes were turned toward that spot where Milton Rhodes and I stood? However, these gloomy thoughts were suddenly broken, but certainly they were not banished. With an acquiescent reply--at any rate, so I thought it--to the angel, the leader abruptly faced us. He placed his bow and arrow upon the ground, slipped over his head the balteus, from which the _corytos_ hung at his right side, drew his sword--it was double-edged, I now noted--from its scabbard, and then he deposited these, too, upon the ground, beside his bow and arrow. His companion was following suit, the two girls standing by motionless and silent. The men advanced a few paces. Each placed his sword-hand over his heart, uttered something in measured and sonorous tones and then bowed low to us--a proceeding, I noted out of the corner of my eye, that not a little pleased our angel. Chapter 23 THAT WE ONLY KNEW THE SECRET