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 “You perceive,” said the captain, “that I employ the Bunzen elements in preference to the Ruhmkorff, which did not answer. The Bunzen elements are fewer, but stronger, as experience has shown. The electricity produced goes to the stern of the vessel, where it acts by means of electro-magnets of great power upon a particular system of levers and gearing, which transmit the motion to the shaft of the screw. Thus, a diameter of six metres, and a pitch of seven and a half, can give me a hundred and twenty revolutions in a second.”

“And you obtain from that?”

“A speed of fifty miles an hour.”

There was some mystery here, but I did not insist upon an explanation. How could electricity yield such a force. Where did this illimitable force take its origin. Was it in the excessive tension obtained by a novel kind of bobbins? Was there in its transmission through the system of levers the power to increase it indefinitely? That was what I could not understand.

“Captain Nemo,” said I, “I see the result, and I do not seek the explanation of the means. I have seen the Nautilus manœuvre before the Abraham Lincoln, and I know its speed. But speed is not everything. You must be able to see whither you are going. You must have the power to direct your course to the right or left—up or down. How do you reach the deeps, where you must support a pressure of hundreds of atmospheres? How do you rise to the surface of the ocean? Finally, how do you maintain your vessel halfway when it suits you to do so? Am I indiscreet in asking all these questions?”