Classic science-fiction writer Jules Verne was amazingly prophetic in foretelling both the design and use of submarines nearly a century before the first nuclear submersibles went to sea
With its imaginative technology, Capt. Nemo's engineering plant for Nautilus is certainly the most extraordinary aspect of his design. On behalf of his nautical protagonist, Verne conceived what was essentially an "all-electric" ship at a time when the first practical applications of electricity were only a few decades old and a century before building any such ships became feasible. In Capt. Nemo's oft-quoted words, "There is a powerful agent, obedient, rapid, facile, which can be put to any use and reigns supreme on board my ship. It does everything. It illuminates our ship, it warms us, it is the soul of our mechanical apparatus. This agent is... electricity."
And indeed, Nautilus uses electricity for cooking, lighting, distilling fresh water, running pumps and other auxiliaries, instrumentation, and, of course, main propulsion. The ship is fitted with a conventional four-bladed propeller at the stern, six meters (20-ft) in diameter and coaxial with the centerline of the hull. Consistent with the relative diameters of the hull and propeller and the freeboard prescribed by Capt. Nemo, Prof. Aronnax observes that when surfaced, the propeller blades occasionally rise above the waves, "beating the water with mathematical precision." Verne has Nemo claiming a speed of 50-kts at 120 revolutions per second -probably in error. One hundred-twenty revolutions per minute makes much more engineering sense for a propeller that size, particularly in view of the type of engine that powers the submarine.
Curiously, the main propulsion engine on Nautilus is not a rotating electric motor. English scientist Michael Faraday (1791-1867) had established the principle of the rotating motor by 1825, and an American blacksmith, Thomas Davenport, had patented a direct-current (DC) motor with all its essentials - rotating coils, a commutator, and brushes - in 1837. Yet, despite the fact that several motor-driven electric vehicles had been demonstrated in both Europe and America by mid-century, Verne's notional design for the prime mover on Nautilus emerges as the electrical analog of a reciprocating steam engine, "where large electromagnets actuate a system of levers and gears that transmit the power to the propeller shaft." In other words, the main engine seems to be mechanically equivalent to a steam engine with "large electromagnets" replacing conventional pistons - a choice that seems strangely backward-looking in light of Verne's technical sophistication.
In contrast, the "breakthrough" that enables Nemo to generate virtually unlimited electrical power extrapolates electrical science so far into the future that only "the willing suspension of disbelief keeps technically-astute readers onboard. Although some hasty writers have wrongly portrayed Nautilus as "nuclear-powered," the actual source for her vast reserves of electricity is described as a hugely scaled-up elaboration of a well-known 19thcentury primary battery, the Bunsen cell. Invented in 1841 by German physicist Robert Bunsen (1811-1899) - better known for devising the "Bunsen burner" - the Bunsen cell uses a carbon cathode in nitric acid and a zinc anode in dilute sulfuric acid, with a porous separator between the liquids. The device generates a potential of 1.89 volts, and later versions added potassium dichromate as a depolarizer.1 Let Capt. Nemo describe his fundamental modification:
"Mixed with mercury, sodium forms an amalgam that takes the place of zinc in Bunsen batteries. The mercury is never consumed, only the sodium is used up, and the sea resupplies me with that. Moreover, I can tell you, sodium batteries are more powerful. Their electric motive (sic) force is twice that of zinc batteries."
Had this actually been tried, the reaction of …