"Forty seconds," said my uncle. "There has elapsed forty seconds between the two words. The sound, therefore, takes twenty seconds to ascend. Now, allowing a thousand and twenty feet for every second--we have twenty thousand four hundred feet--a league and a half and one-eighth." These words fell on my soul like a kind of death knell. "A league and a half," I muttered in a low and despairing voice. .......... "It shall be got over, my boy," cried my uncle in a cheery tone; "depend on us." .......... "But do you know whether to ascend or descend?" I asked faintly enough. .......... "We have to descend, and I will tell you why. You have reached a vast open space, a kind of bare crossroad, from which galleries diverge in every direction. That in which you are now lying must necessarily bring you to this point, for it appears that all these mighty fissures, these fractures of the globe's interior, radiate from the vast cavern which we at this moment occupy. Rouse yourself, then, have courage and continue your route. Walk if you can, if not drag yourself along--slide, if nothing else is possible. The slope must be rather rapid--and you will find strong arms to receive you at the end of your journey. Make a start, like a good fellow." These words served to rouse some kind of courage in my sinking frame. "Farewell for the present, good uncle, I am about to take my departure. As soon as I start, our voices will cease to commingle. Farewell, then, until we meet again." .......... "Adieu, Harry--until we say Welcome." Such were the last words which reached my anxious ears before I commenced my weary and almost hopeless journey. This wonderful and surprising conversation which took place through the vast mass of the earth's labyrinth, these words exchanged, the speakers being about five miles apart--ended with hopeful and pleasant expressions. I breathed one more prayer to Heaven, I sent up words of thanksgiving--believing in my inmost heart that He had led me to the only place where the voices of my friends could reach my ears. This apparently astounding acoustic mystery is easily explainable by simple natural laws; it arose from the conductibility of the rock. There are many instances of this singular propagation of sound which are not perceptible in its less mediate positions. In the interior gallery of St. Paul's, and amid the curious caverns in Sicily, these phenomena are observable. The most marvelous of them all is known as the Ear of Dionysius. These memories of the past, of my early reading and studies, came fresh to my thoughts. Moreover, I began to reason that if my uncle and I could communicate at so great a distance, no serious obstacle could exist between us. All I had to do was to follow the direction whence the sound had reached me; and logically putting it, I must reach him if my strength did not fail.