"Yes," he replied, "but the conditions in the different directions are dissimilar. In the direction of the Kentucky cavern, the passage is tortuous, and often contracts to a narrow crevice. In one place near the cavern's mouth, as you will remember, we had to dive beneath the surface of a stream of water. That stratum of water as effectually closed the exit from the earth as the stopper prevents water escaping from a bottle. Between the point we now occupy and that water stopper, rest thousands of miles of quiescent air. The inertia of a thousand miles of air is great beyond your comprehension. To move that column of air by pushing against this end of it, and thus shoving it instantly out of the other end, would require greater force than would burst the one hundred and fifty miles of inelastic stone above us. Then, the friction of the sides is another thing that prevents its accomplishment. While a gradually applied pressure would in time overcome both the inertia of the air and the friction of the stone passages, it would take a supply of energy greater than you can imagine to start into motion the elastic mass that stands as solid and immovable as a sentinel of adamant, between the cavern you entered, and the spot we now occupy. Time and energy combined would be able to accomplish the result, but not under present conditions. "In the other direction a broad open channel reaches directly to and connects with the volcanic shaft. Through this channel the air is in motion, moving towards the extinct crater, being supplied from another surface orifice. The gases liberated in the manner I have described, naturally follow the line of least resistance. They turn at once away from the inert mass of air that rests behind us, and move with increasing velocity towards the volcanic exit. Before the pressure that might be exerted towards the Kentucky cavern would have more than compressed the intervening column of air enough to raise the water of a well from its usual level to the surface of the earth, the velocity in the other direction would have augmented prodigiously, and with its increased rapidity a suction would follow more than sufficient to consume the increasingly abundant gases from behind." "Volcanoes are therefore local, and the interior of the earth is not a molten mass as I have been taught," I exclaimed.