“But it seems as if you’ve explained everything.”

“I’ve not explained the inverse square law.”

“You’ve a proof right there saying that if gravity follows an inverse square law, satellites move on conic sections.”

“And Flamsteed says that they do,” Isaac said, yanking the sheaf of notes out of Daniel’s hip pocket. Ignoring the cover letter, he tore the ribbon from the bundle and began to scan the pages. “Therefore gravity does indeed follow an inverse square law. But we may only say so because it is consistent with Flamsteed’s observations. If tonight Flamsteed notices a comet moving in a spiral, it shows that all my work is wrong.”

“You’re saying, why do we need Flamsteed at all?”

“I’m saying that the fact that we do need him proves that God is making choices.”

“Or has made them.”

This caused a sort of queasy sneer to come across Isaac’s face. He closed his eyes and shook his head. “I am not one of those who believes that God made the world and walked away from it, that He has no further choices to make, no ongoing presence in the world. I believe that He is everywhere, making choices all the time.”

“But only because there are certain things you have not explained yet with geometric proofs.”

“As I told you, I seek God where Geometry fails.”

“But perhaps there is an undiscovered proof for the inverse square law. Perhaps it has something to do with vortices in the ?ther.”

“No one has been able to make sense of vortices.”

“Some interaction of microscopic particles, then?”

“Particles traversing the distance from the Sun to Saturn and back, at infinite speed, without being hindered by the ?ther?”

“You’re right, it is impossible to take seriously. What is your hypothesis, Isaac?”

“ Hypothesis non fingo.”

“But that’s not really true. You begin with a hypothesis-I saw several of them scratched in the gravel out there. Then you come up with one of these diagrams. I cannot explain how you do that part, unless God is using you as a conduit. When you are finished, it is no longer a hypothesis but a demonstrated truth.”

“Geometry can never explain gravity.”

“Calculus then?”

“The calculus is just a convenience, a short-hand way of doing geometry.”

“So what is beyond geometry is also beyond calculus.”

“Of course, by definition.”

“The inner workings of gravity, you seem to be saying, are beyond the grasp, or even the reach, of Natural Philosophy. To whom should we appeal, then? Metaphysicians? Theologians? Sorcerers?”

“They are all the same to me,” Isaac said, “and I am one.”

IT WAS AS IFWILLIAMof Orange had searched the world over to find the place most different from Versailles, and had told Eliza to meet him there. At Versailles, everything had been designed and made by men. But here was nothing to see but ocean and sand. Every grain of sand had been put where it was by waves that formed up in the ocean according to occult laws that might have been understood by the Doctor, but not by Eliza.

She had dismounted and was leading her horse northwards up the beach. The sand was hard-packed and solid and wet, speckled all over with cockle shells in colors and patterns of such profusion and variety that they must have given the first Dutchmen the idea to go out into the sea and bring back precious things from afar. They made a welcome contrast against the extreme flatness and sameness of beach, water, and misty sky, and exerted a hypnotic effect on her. She forced herself to look up from time to time. But the only feature of the view that ever changed was the signatures of foam deposited on the beach by the waves.

Each breaker, she supposed, was as unique as a human soul. Each made its own run up onto the shore, being the very embodiment of vigor and power at the start. But each slowed, spread thin, faltered, dissolved into a hissing ribbon of gray foam, and got buried under the next. The end result of all their noisy, pounding, repetitious efforts was the beach. Seen through a lens, the particular arrangement of sand-grains that made up the beach presumably was complicated, and reflected the individual contributions of every single wave that had ended its life here; but seen from the level of Eliza’s head it was unspeakably flat, an “abomination of desolation in a dark place,” as the Bible would put it.

She heard a ripping noise behind her and turned around to look to the south, toward the dent in the beach, several miles distant, that formed the harbor of Scheveningen. The last time she’d looked back, a few minutes ago, there had been nothing between her and the anchorage but a few clam-diggers. But now there was a sail on the sand: a triangle of canvas, stretched drum-tight by the wet wind off the sea. Below it hovered a spidery rig of timbers with spoked wagon-wheels at their ends. One wheel was suspended in the air by the heeling of the vehicle. Taken together with the speed of its progress up the beach, this created the impression that it was flying. The wheel spun slowly in the air, dripping clots of wet sand from its rim, which was very wide so that it rolled over, instead of cutting into, the sand and its gay mosaic of cockle shells. The opposite wheel was scribing a long fat track down the beach, slaloming between the dark hunched forms of the diggers; though, a hundred yards in its wake, this trace had already been erased by the waves.

A fishing-boat had eased in to shore as the tide ebbed, pulled up her sideboards, and allowed herself to be stranded there. The fishermen had chocked her upright with baulks of wood, brought their catch up out of the hold, and laid it out on the sand, creating a little fish-market that would last until the tide flowed in again, chased away the customers, and floated the boat. People had carried baskets out from town, or driven out in carriages, to carry out disputes with the fishermen over the value of what they’d brought back from the deep.

Some of them turned to look at the sand-sailer. It rushed past Eliza, moving faster than any horse could gallop. She recognized the man operating the tiller and manipulating the lines. Some of the fish-buyers did, too, and a few of those bothered to doff their hats and bow. Eliza mounted her horse and rode in pursuit.

The view inland was blocked by dunes. Not dunes such as Eliza had once seen in the Sahara, but hybrids of dunes and hedges. For these were covered by, and anchored in, vegetation that was light green in the lower slopes, but in other places deepened to a bluish cast, and formed up into great furry dark eyebrows frowning at the sea.

A mile or so north of where the fishing-boat had been beached, the sight-line from the town was severed by a gradual bend in the coastline, and a low spur flung seawards by a dune. From here, the only sign that Holland was a settled country was a tall watchtower with a conical roof, built atop a dune, perhaps half a mile distant. The sand-sailer had come to rest, its sheets loosened so that the sail reached and weathercocked.

“I am probably meant to ask, ‘Where is your Court, O Prince, your entourage, your bodyguards, your train of painters, poets, and historians?’ Whereupon you’d give me a stern talking-to about the decadence of France.”

“Possibly,” said William, Prince of Orange and Stadholder of the Dutch Republic. He had extricated himself from the canvas seat of the sailer and was standing on the beach facing out to sea, layers of sand-spattered leather and spray-soaked wool giving his body more bulk than it really had. “Or perhaps I like to go sand-sailing by myself, and your reading so much into it is proof you’ve been too long at Versailles.”