"ES," repeated Mr. Curtis, bringing down his fist with a bang, "that 's where the real difficulty lies; that 's where the impossibility arises. The other obstacles might perhaps be overcome if sufficient time and money were devoted to the work. But the great question is, How will you manage when you reach the center of the earth, where the materials are one mass of liquid fire? Answer me that!"

"How do you know the earth is a mass of liquid fire at the center?" inquired the doctor, coolly.

"How do I know it? Why, all the best authorities concede the fact."

"Indeed, I was not aware of it. On the contrary, I thought that our most profound thinkers all rejected this theory."