"By the want of coal, which may justly be called the most precious of minerals."
"Yes, the most precious indeed," replied the engineer; "and it would seem that nature wished to prove that it was so by making the diamond, which is simply pure carbon crystallized."
"You don't mean to say, captain," interrupted Pencroft, "that we burn diamonds in our coal stoves?"
"No, my friend," replied Harding.
"However," resumed Gideon Spilett, "you do not deny that some day the coal will be entirely consumed?"
"Oh! the veins of coal are still considerable, and the hundred thousand miners who annually extract from them a hundred millions of hundredweights have not nearly exhausted them."
"With the increasing consumption of coal," replied Gideon Spilett, "it can be foreseen that the hundred thousand workmen will soon become two hundred thousand, and that the rate of extraction will be doubled."
"Doubtless; but after the European mines, which will be soon worked more thoroughly with new machines, the American and Australian mines will for a long time yet provide for the consumption in trade."
"For how long a time?" asked the reporter.
"For at least two hundred and fifty or three hundred years."
"That is reassuring for us, but a bad lookout for our great grandchildren!" observed Pencroft.
"They will discover something else," said Herbert.
"It is to be hoped so," answered Spilett, "for without coal there would be no machinery, and without machinery there would be no railways, steamers, manufactories, nothing of all that is indispensable to modern civilization!"
"But what will they find?" asked Pencroft. Can you guess, captain?"
"Nearly, my friend."
"And what will they burn instead of coal?"
"Water," replied Harding.
"Water!" cried Pencroft, "water as fuel for steamers and engines! water to heat water!"
"Yes, but water decomposed into its primitive elements," replied Cyrus Harding, "and decomposed, doubt-
