“Pencroft: ‘And what will they burn instead of coal?’ Harding: ‘Water. But water decomposed into its primitive elements… yes, my friends, I believe that water will some day be employed as fuel, that hydrogen and oxygen which constitute it… will furnish an inexhaustible source of heat and light… Some day water will be the coal of the future.’”
Jules Verne, The Mysterious Island, 1874.