Sound does not possess the property of traveling with such extreme rapidity. Besides the density of the air at that depth from light and motion was very far from adding to the rapidity of circulation. Several seconds elapsed, which to my excited imagination, appeared ages; and these words reached my eager ears, and moved my wildly beating heart: "Harry, my boy, is that you?" A short delay between question and answer. "Yes--yes." .......... "Where are you?" .......... "Lost!" .......... "And your lamp?" .......... "Out." .......... "But the guiding stream?" .......... "Is lost!" .......... "Keep your courage, Harry. We will do our best." .......... "One moment, my uncle," I cried; "I have no longer strength to answer your questions. But--for heaven's sake--do you--continue--to speak--to me!" Absolute silence, I felt, would be annihilation. "Keep up your courage," said my uncle. "As you are so weak, do not speak. We have been searching for you in all directions, both by going upwards and downwards in the gallery. My dear boy, I had begun to give over all hope--and you can never know what bitter tears of sorrow and regret I have shed. At last, supposing you to be still on the road beside the Hansbach, we again descended, firing off guns as signals. Now, however, that we have found you, and that our voices reach each other, it may be a long time before we actually meet. We are conversing by means of some extraordinary acoustic arrangement of the labyrinth. But do not despair, my dear boy. It is something gained even to hear each other." While he was speaking, my brain was at work reflecting. A certain undefined hope, vague and shapeless as yet, made my heart beat wildly. In the first place, it was absolutely necessary for me to know one thing. I once more, therefore, leaned my head against the wall, which I almost touched with my lips, and again spoke. "Uncle." .......... "My boy?" was his answer after a few moments. .......... "It is of the utmost consequence that we should know how far we are asunder." .......... "That is not difficult." .......... "You have your chronometer at hand?" I asked. .......... "Certainly." .......... "Well, take it into your hand. Pronounce my name, noting exactly the second at which you speak. I will reply as soon as I hear your words--and you will then note exactly the moment at which my reply reaches you." .......... "Very good; and the mean time between my question and your answer will be the time occupied by my voice in reaching you." .......... "That is exactly what I mean, Uncle," was my eager reply. .......... "Are you ready?" .......... "Yes." .......... "Well, make ready, I am about to pronounce your name," said the Professor. I applied my ear close to the sides of the cavernous gallery, and as soon as the word "Harry" reached my ear, I turned round and, placing my lips to the wall, repeated the sound. ..........