n to say, captain," interrupted Pencroft, "that we burn
diamonds in our stoves in the shape of coal?"

"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 look-out for our great
grandchildren!" observed Pencroft.

[Illustration: WINTER EVENINGS IN GRANITE HOUSE]

"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, no steamers, no manufactories, nothing of that which is
indispensable to modern civilisation!"

"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, doubtless; by electricity, which will then
have become a powerful and manageable force, for all great
discoveries, by some inexplicable law, appear to agree and become
complete at the same time. Yes, my friends, I believe that water will
one day be employed as fuel, that hydrogen and oxygen which constitute
it, used singly or together, will furnish an inexhaustible source of
heat and light, of an intensity of which coal is not capable. Some day
the coal-rooms of steamers and the tenders of locomotives will,
instead of coal, be stored with these two condensed gases, which will
burn in the furnaces with enormous calorific power. There is,
therefore, nothing to fear. As long as the earth is inhabited it will
s