“My legs aren’t quite as limber as they were in my youth,” she said with a wince. Then grasping a brass ring set in a section of the floorboards, she pulled up a section of the planks, revealing the rotating crankshaft.
Raven craned his neck to see the mechanics, curious to observe the workings of the engine.
Mrs. Guppy caught his movement and regarded him thoughtfully. “Would you like to have a closer look?”
Another shrug, but she must have seen the flare of interest in his eyes, for she beckoned him to crouch down beside mademoiselle. “Come, have a look. You have my word that my men won’t lay a hand on you.”
He hesitated, and then decided that if she had intended to toss him overboard, she would have tried to do so already. He slid closer and dropped to a crouch—but kept himself poised to spring up at the first sign of trouble. Already he had a plan for scrambling out on the narrow deck of the prow, where the two men could not both come at him at once.
“It’s really a rather simple contraption,” began Mrs. Guppy. “The boiler heats water, which creates steam. The steam creates pressure, which opens and closes the pistons as they move up and down. There are gears and levers, which then move in different ways to convert that force to turn the propeller. And that is what pushes the boat through the water.”
Raven watched the rhythmic up-and-down motion of the pistons with great interest. Beneath his boots he could feel the vibration of the crankshaft thrumming though the floorboards.
“So, the pistons go up and down,” he mused.
“Correct,” said Mrs. Guppy.
Raven moved his forefinger in a circling motion. “And a propeller has to spin round and round.”
“That’s right. In engineering, we call it converting reciprocating motion into rotational motion.”
“So, how does that happen?”
He knew the answer in principle, but as he had yet to see a working marine engine in action, he was curious to observe exactly how all the individual parts moved.
The boatman made a rude sound. “Next you’ll be lecturing the little muckworm on Newton’s Laws of Motion.”
“Actually, I have a feeling that the lad would catch on very quickly.” Mrs. Guppy turned back to Raven. “By the by, do you have any formal education? Can you read?”
Raven let out a snicker. “Do I look like I know m’letters?”
“Appearances can be deceiving,” she murmured.
Raven froze on hearing one of Charlotte’s favorite warnings, suddenly aware that he must not underestimate the plain and dowdy Mrs. Guppy. Dressed in an unflattering shade of mud-brown wool, she looked like a rather dull greengrocer’s wife. But clearly she was not.
He gave a rude grunt, determined to be more careful and keep his mouth shut.
“The lad asked a good question.” Tucking her skirts more tightly around her legs, mademoiselle shifted her position. “Please continue with your explanation.”
“If you take a closer look at the engine, you see there is a system of connecting rods and levers . . .”
Raven and Mademoiselle Benoit listened with rapt attention as Mrs. Guppy began to explain the mechanics of all the moving parts, both of them interrupting to ask questions.
“You’reveryclever.” Mademoiselle smiled after Raven inquired about the arrangement of gears turning the crankshaft.
He ducked his head, once again aware that he ought not appear too clever.
Mrs. Guppy eyed him for a long moment and then resumed explaining how the technology worked.
The tide was turning, the crosscurrents churning up rippling eddies as the boat passed under Blackfriars Bridge.
“Avast, Jed, cut the steam,” called Andrew over the thump of the pistons. “White Lion Wharf is just ahead.”
Mademoiselle Benoit sat back, her look of enthusiasm giving way to naked fear.
“You must be brave,” counseled Mrs. Guppy. “We will soon be with Oliver, and the three of us will come up with an idea of how to deal with the latest development.”
“But what if . . .” Mademoiselle turned away, leaving the rest of her words unsaid.
