Gregory's Server“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,”
[...]
"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."
[...]
"Water will be the coal of the future."
--
Jules Verne, "The Mysterious Island" Part 2, Chapter 11
published 1875.
I just love this mans visions. He was predicting so much stuff back then.