"…And what will they burn instead of coal?"
"Water," replied Cyrus 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 laws, 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 coalrooms 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 supply the wants of its inhabitants, and there will be no want of either light or heat as long as the productions of the vegetable, mineral or animal kingdoms do not fail us. I believe, then, that when the deposits of coal are exhausted we shall heat and warm ourselves with water. Water will be the coal of the future."
"I should like to see that," observed the sailor.
"You were born too soon, Pencroft," returned Neb, who only took part in the discussion by these words…
Cyrus Harding, the imaginary hero of Julie Vern from the novel "The Mysterious Island" (1874) who was the first that "talked" about the production of hydrogen energy!