At the wharf they descended from the litter and boarded the ship by way of its extra-long gangplank. The addition of the huge side wheels meant that the ship itself could not directly abut the stone wharf. The main deck of the vessel was as unconventional as the rest. It was very narrow, in order to make room for immense, inboard wheels that corresponded to those on the outside of the ship. These wheels were hollow frameworks, and they contained men.
"I confess," Selene said, "to utter mystification."
A man in a philosopher s ragged tunic came forward, his face wreathed in that self-satisfied smile she had come to know so well. He bowed and waited to be addressed.
"Good afternoon, Chilo," said the queen. "What new miracle have you to show me today?"
"As so often, my queen," he said, "there is little new about it. It is a novel application for the common water-raising wheel used in irrigation operations."
"I had noticed the resemblance," she said. "Why one needs irrigation wheels on a ship is not obvious."
"It has to do with our researches into the properties of energy," he said earnestly. "There is a relationship between force exerted in one direction and another force, or perhaps the same force, in another direction. We feel that there is a principle—"
"Quite fascinating, I am sure," the queen interrupted. "You must be sure to tell me all about it when you have it all figured out. In the meantime, if you could just show me how wheels benefit a ship?"
"Of course, Majesty, of course. Well, the outer structure is not precisely a wheel. I have termed it a 'rotary oar.' You see the boards protruding from its perimeter? These are paddles, and they perform the same function as a conventional oar, except that they work in a vertical plane, instead of the horizontal, or, rather the elliptical-horizontal plane of an oar."
"Chilo," Scipio said, "why not just get it moving? The principle of the thing will be instantly appreciable to Her Majesty then."
"I suppose so," Chilo said, disappointed.
"Now he'll sulk," Selene said when the philosopher went off to give his orders to the crew. "There is nothing sadder than a philosopher cheated of a chance to lecture."
Among the ship's petty officers there was a barking of orders and a popping of whips, and a piper began to play a rhythmic tune on his double flute. Within the inboard wheels, men began climbing rungs as if ascending a ladder. The outboard wheels started to turn, churning the water. The ship commenced a slow movement. It drew away from the wharf and moved out into the harbor amid a great creaking of machinery.
"You see," Chilo explained, "the vertical motion of the slaves climbing is transformed into the rotary motion of the inboard wheel turning. This is in turn transmitted to the outboard wheel, causing the paddles to push against the water, propelling the ship forward. By turning around and climbing the rear of the wheel, the slaves can cause the ship to move backward. Direction can be controlled by causing one wheel to move more slowly than the other, and the steering oar can be used for minor corrections. By working the wheels in opposite directions, the ship can spin quickly on its axis."
"Very ingenious," the queen allowed. "But oared ships can do all these things, and have for centuries. What is the advantage of these wheels?"
"There are several," Marcus Scipio informed her. "In the first place, you need far fewer slaves to turn these wheels than to man oars. A ship this size would require at least three hundred, with plenty of relief rowers. Thirty or forty slaves are all you need to man these wheels. They eat far less and that makes for longer voyages."
"And," said Flaccus, "rowers must be highly skilled. They are expensive and are not replaced easily. Totally, unskilled slaves and convicts can turn these wheels. Nothing is required except for a sound pair of legs."
"They can't be deaf," Marcus pointed out. "They have to be able to hear the flute."
Flaccus nodded. "That is true."
"If a wheel is damaged in battle," Selene pointed out, "it wouldn't be easy to replace, not like a damaged oar."
"This vessel is a prototype built to test the design," Chilo said. "For a warship, the wheels will have armored cowlings. Only the part that actually touches the water need be exposed." He looked at her expectantly.
"Very well," she said at last, "you may proceed with this project. What is the next phase?"
"Trials on the open sea, Your Majesty," Chilo told her. "These can proceed immediately, with this experimental vessel. Upon successful conclusion, a full-sized armed and manned warship will be built and tested. If all goes well, as I am sure it will, a flotilla will be constructed and deployed."