Part 5 (1/2)
”If we follow the usual proportion,” replied Morgan, ”a diameter of 108 inches would require sides of two feet thickness, or less.”
”That would be too much,” replied Barbicane; ”for you will observe that the question is not that of a shot intended to pierce an iron plate; it will suffice to give it sides strong enough to resist the pressure of the gas. The problem, therefore, is this-- What thickness ought a cast-iron sh.e.l.l to have in order not to weight more than 20,000 pounds? Our clever secretary will soon enlighten us upon this point.”
”Nothing easier.” replied the worthy secretary of the committee; and, rapidly tracing a few algebraical formulae upon paper, among which _n_^2 and _x_^2 frequently appeared, he presently said:
”The sides will require a thickness of less than two inches.”
”Will that be enough?” asked the major doubtfully.
”Clearly not!” replied the president.
”What is to be done, then?” said Elphinstone, with a puzzled air.
”Employ another metal instead of iron.”
”Copper?” said Morgan.
”No! that would be too heavy. I have better than that to offer.”
”What then?” asked the major.
”Aluminum!” replied Barbicane.
”Aluminum?” cried his three colleagues in chorus.
”Unquestionably, my friends. This valuable metal possesses the whiteness of silver, the indestructibility of gold, the tenacity of iron, the fusibility of copper, the lightness of gla.s.s. It is easily wrought, is very widely distributed, forming the base of most of the rocks, is three times lighter than iron, and seems to have been created for the express purpose of furnis.h.i.+ng us with the material for our projectile.”
”But, my dear president,” said the major, ”is not the cost price of aluminum extremely high?”
”It was so at its first discovery, but it has fallen now to nine dollars a pound.”
”But still, nine dollars a pound!” replied the major, who was not willing readily to give in; ”even that is an enormous price.”
”Undoubtedly, my dear major; but not beyond our reach.”
”What will the projectile weigh then?” asked Morgan.
”Here is the result of my calculations,” replied Barbicane.
”A shot of 108 inches in diameter, and twelve inches in thickness, would weigh, in cast-iron, 67,440 pounds; cast in aluminum, its weight will be reduced to 19,250 pounds.”
”Capital!” cried the major; ”but do you know that, at nine dollars a pound, this projectile will cost----”
”One hundred and seventy-three thousand and fifty dollars ($173,050).
I know it quite well. But fear not, my friends; the money will not be wanting for our enterprise. I will answer for it. Now what say you to aluminum, gentlemen?”
”Adopted!” replied the three members of the committee. So ended the first meeting. The question of the projectile was definitely settled.
CHAPTER VII