The four members of the committee each swallowed a dozen sandwiches,
followed by a cup of tea, and the debate recommenced.

"Our cannon," said Barbicane, "must be possessed of great tenacity,
great hardness; it must be infusible by heat, indissoluble, and
inoxydable by the corrosive action of acids."

"There is no doubt about that," answered the major, "and as we shall
have to employ a considerable quantity of metal we shall not have much
choice."

"Well, then," said Morgan, "I propose for the fabrication of the
Columbiad the best alloy hitherto known--that is to say, 100 parts of
copper, 12 of tin, and 6 of brass."

"My friends," answered the president, "I agree that this composition has
given excellent results; but in bulk it would be too dear and very hard
to work. I therefore think we must adopt an excellent material, but
cheap, such as cast-iron. Is not that your opinion, major?"

"Quite," answered Elphinstone.

"In fact," resumed Barbicane, "cast-iron costs ten times less than
bronze; it is easily melted, it is readily run into sand moulds, and is
rapidly manipulated; it is, therefore, an economy of money and time.
Besides, that material is excellent, and I remember that during the war
at the siege of Atlanta cast-iron cannon fired a thousand shots each
every twenty minutes without being damaged by it."