“Yes.”
… …
“Now, attention. I am going to call your name.”
…
I put my ear to the wall, and as soon as the name “Axel” came I immediately replied “Axel,” then waited.
…
“Forty seconds,” said my uncle. “Forty seconds between the two words; so the sound takes twenty seconds in coming. Now, at the rate of 1,120 feet in a second, this is 22,400 feet, or four miles and a quarter, nearly.”
…
“Four miles and a quarter!” I murmured.
…
“It will soon be over, Axel.”
…
“Must I go up or down?”
…
“Down—for this reason: We are in a vast chamber, with endless galleries. Yours must lead into it, for it seems as if all the clefts and fractures of the globe radiated round this vast cavern. So get up, and begin walking. Walk on, drag yourself along, if necessary slide down the