“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 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 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. However, it was not Neb’s speech which interrupted the conversation, but Top’s barking, which broke out again with that strange intonation which had before perplexed the engineer. At the same time Top began to run round the mouth of the well, which opened at the extremity of the interior passage. “What can Top be barking in that way for?” asked Pencroft. “And Jup be growling like that?” added Herbert. In fact the orang, joining the dog, gave unequivocal signs of agitation, and, singular to say, the two animals appeared more uneasy than angry. “It is evident,” said Gideon Spilett, “that this well is in direct communication with the sea, and that some marine animal comes from time to time to breathe at the bottom.” “That’s evident,” replied the sailor, “and there can be no other explanation to give. Quiet there, Top!” added Pencroft, turning to the dog, “and you, Jup, be off to your room!” The ape and the dog were silent. Jup went off to bed, but Top remained in the room, and continued to utter low growls at intervals during the rest of the evening. There was no further talk on the subject, but the incident, however, clouded the brow of the engineer.