machinery," returned James Curtis, the first speaker. "But machinery is n't everything. Of course I won't deny that you could dig a well a few thousand feet deep; but all efforts to go much beyond this depth would be unavailing, since the walls would continually cave in, burying your workmen under an enormous mass of earth and stones."
"And so you suppose that I would stand by with folded arms, and allow the walls to cave in, do you?"
"I don't see how you could help yourself."
"Nothing will be easier. As fast as I dig, I shall have a stout metal tube cast, of the size of my well, and let it down to support the walls. In that way all danger of caving in will be avoided."
"Well, admitting, for the sake of argument, that you can make machinery powerful enough to dig through miles of solid rock, and allowing that you could prevent the walls from caving in, even so, I hardly see that you would be very much more advanced than you were before."
"And why not, pray!"
"Because you seem to forget that the earth, at the center, is one mass of liquid fire. So that, even if you succeeded in boring down through
