A silence ensued. I sank into profound and gloomy meditation. Four thousand feet down. A mile deeper, and where would we be? The prospect certainly was, from any point of view, dark and mysterious enough, dark and mysterious enough, forsooth, to satisfy the wildest dream of a Poe or a Doré. To imagine a Dante's Inferno, however, is one thing, and to find yourself in it is quite another. These are things, by the way, that should not be confounded. 'Tis true, we weren't in it yet; but we were on our way. I hasten to say, though, that I had no thoughts of turning back. No such thought, even the slightest, was entertained for one single moment. I did not blink, that was all. I believed our enterprise was a very dangerous one; I believed it was very probable that we should never return to the light of the sun. Such thoughts are not pleasant, are, indeed, horrible. And yet, in the very horror of them, I found a strange fascination. Yes, we might leave our bones in this underground world, in this very gallery even. Even so, we should have our own exceeding great reward. For ours would be the guerdon of dying in a stranger, a more wonderful quest than any science or discovery ever had known. A strange reward, you say mayhap, and perhaps you wonder what such a reward can mean to a dying or a dead man. All I have to say is that, if you do, you know naught of that flaming spirit which moves the scientist and the discoverer, that such as you should never--indeed, can ever--seek the dread secrets of Nature or journey to her hidden places. We rested there for exactly one hour. The temperature, by the way, was 57° Fahrenheit. When we resumed the descent, I was using the phosphorus-lamp instead of the electric one. It was not likely that even our electric lights would fail us; still there was no guessing what might happen, and it might be well, I thought, to adopt a policy of light-conservation also. As for the phosphorus lamps, these would furnish light for _six months_. In this, they were simply wonderful; but there was one serious drawback: the light emitted was a feeble one. The manufacture of this lamp (at one time used, I believe, in Paris, and probably elsewhere, in magazines containing explosives) is simplicity itself. Into a glass phial is put a small piece of phosphorus. The phial is filled two-thirds full of olive-oil, heated to the boiling point. The thing is hermetically corked, and there you are. When you wish to use your wonderful little pharos, you simply allow air to enter. The space above the oil becomes luminous then. You replace the cork, and the phial remains sealed until there is occasion to restore the waning light, which you do, of course, by allowing more air to enter. As has been said, such a phial will furnish light for a half-year.