"Now," said Elphinstone, "what thickness must we give its sides?"
"A thickness of six feet," answered Barbicane.
"You do not think of raising such a mass upon a gun-carriage?" asked the major.
"That would be superb, however! said J.T. Maston.
"But impracticable," answered Barbicane. "No, I think of casting this engine in the ground itself, binding it up with wrought-iron hoops, and then surrounding it with a thick mass of stone and cement masonry. When it is cast it must be bored with great precision so as to prevent windage, so there will be no loss of gas, and all the expansive force of the powder will be employed in the propulsion."
"Hurrah! hurrah!" said Maston, "we have our cannon."
"Not yet," answered Barbicane, calming his impatient friend with his hand.
"Why not?"
"Because we have not discussed its form. Shall it be a cannon, howitzer, or a mortar?"
"A cannon," replied Morgan.