Another door whacked open and in came Leibniz. He bowed to the ladies, looking very solemn. “I take it that a departure for Hanover is planned, and soon,” he said. “If your royal highness will have me, I will accompany you.” He turned toward Eliza. “My lady. The friendship that began in Leipzig thirty years ago, when our paths crossed at the Fair, and I shared a little adventure with you and your Vagabond beau-”

“Aha!” shouted Caroline.

“Draws now to a close. The Princess’s noble and splendid attempt to effect a philosophical reconciliation-so ably and patiently assisted by Dr. Waterhouse-has, I am sorry to say-”

“Failed?” said Caroline.

“Adjourned,” Leibniz said.

“For how long?”

“Hundreds, perhaps thousands of years.”

“Hmm,” said Caroline, “that will be of little practical utility to the House of Hanover, when it comes time to select a new Privy Council.”

“I am sorry,” said Leibniz, “but there is no rushing certain things. While other matters, such as my departure from London, happen entirely too soon.”

“Where are Sir Isaac, and Dr. Waterhouse?” the Princess inquired.

“Sir Isaac has taken his leave, and forwards apologies for not having said good-bye in person,” said Leibniz, “but one gets the idea he had terribly important things to do. Dr. Waterhouse said he would await you in the garden, just in case you might be of a mind to behead him for failing in his mission.”

“By no means! I shall go and thank him for his good offices-and I’ll see you on the boat tomorrow!” said Caroline, and swept out of the place.

“Eliza,” said the savant.

“Gottfried,” said the Duchess.

“IT WAS NOT HALF so blubbery as it might have been,” said Leibniz, “when one considers how long the Duchess and I have known each other, and all we have been through, and whatnot. We shall keep in touch, of course, through letters.”

He was describing his leave-taking from Eliza at Leicester House the day before; but he might as well have been talking of the one that was happening now, on London Bridge, between him and Daniel.

“Forty-one years,” Daniel said.

“I was thinking the same thing!” Leibniz said, practically before Daniel had got the words out. “It was forty-one years ago when you and I first met, right here, on this very what-do-you-call-it.”

“Starling,” Daniel said. They were standing on the one beneath the Square, near the mid-point of the Bridge, and not awfully far from the Main-Topp where the Clubb had of late conducted its Stake-out. But Daniel’s memory of that, though only a few weeks old, was already quite washed-out and indistinct compared to what Leibniz was speaking of: the day in 1673 when a young Leibniz (no Baron in those days) with an Arithmetickal Engine tucked under his arm had disembarked from a ship that had brought him over from Calais, and been conveyed to this starling-to this very spot-by a lighter, and first made the acquaintance of young Daniel Waterhouse of the Royal Society.

Leibniz’s memory was no less distinct. “I believe it was-here!” (tapping a flat rock at starling’s edge with his toe) “where I first touched down.”

“That is how I remember it.”

“Of course we are both wrong, if Absolute Space is correct,” Leibniz went on. “For during those forty-one years the Earth has rotated, and revolved about the Sun, and the Sun, for all we know, has careered for some vast distance. So I did not really touch down here but in some other place that is now far out in the interstellar vacuum.”

Daniel did not rise to this bait. He was fearful that Leibniz was about to burst out into some bitter declamation against Newton and Newton’s philosophy. But Leibniz drew back from that brink, even as he was drawing back from the stony rim of the starling. A longboat was working up towards them. It was the lighter that would take Leibniz out to the Hanoverian sloop Sophia, where Princess Caroline had already settled into her cabin.

“What do I remember of that day? We were espied, and glared at, by Hooke, who was over yonder surveying a wharf,” said Leibniz, pointing at the London bank. “We went to pay a call on poor old Wilkins, who lay some great responsibility on your shoulders-”

“He wanted me to ‘make it all happen,’ ” said Daniel.

Leibniz laughed. “What do you suppose the rascal meant by that?”

“I have thought about it a million times,” said Daniel. “Religious toleration? The Royal Society? Pansophism? The Arithmetickal Engine? I cannot be sure. But all of those things were linked together in Wilkins’s mind.”

“He had a prefiguring of what Caroline calls the System of the World.”

“Perhaps. At any rate, I have tried to preserve in my mind, since then, that linkage-the notion that all of those things must move together, somewhat like prisoners on a common chain-”

“A cheerful image!” Leibniz remarked.

“And if there has been any plan whatever to my life in those forty-one years, it’s been that I have tried to keep an eye out for whichever of them was lagging farthest behind, and chivvy it along. For two decades, the laggard has been Arithmetickal Engines and Logic Mills, et cetera.”

“And so you have toiled on that,” said Leibniz, “for which you have my ?ternal gratitude. But who knows? With the support of the Tsar, and the motive Power of the Engine for Raising Water by Fire, perhaps it shall be laggardly no more.”

“Perhaps,” said Daniel. “It grieves me, now-especially since yesterday-that I went off into seclusion, and did not involve myself in the Metaphysickal rift until it was too late.”

“But if you had, you’d be now berating yourself over having neglected some other matter-good Puritan that you are.”

Daniel snorted.

“Remember that in those days Newton was known chiefly as a very clever telescope-maker,” Leibniz went on. “Wilkins could not have foreseen the rift you spoke of-and so could not have charged you with healing it. You are clear of any such burthen.”

“But the grand project of Pansophism was a thing he saw very clearly, and, I’m sure, wanted me to support in whatever way I could,” Daniel said. “I wonder now if I did the best possible job of it.”

“And I should say the answer is yes,” said Leibniz, “for that we live in the best of all possible worlds.”

“I hope that is not true,” said Daniel, “as it seems to me now that my journey here from Boston, which I confess I undertook with a certain kind of foolish and thrilling hope in my heart, has concluded in tragedy-and not even grand tragedy but something much more futile and ignominious.”

“After we visited Wilkins on his death-bed,” said Leibniz, “we went to a coffee-house, did we not, and talked. We spoke of Mr. Hooke’s observations of snowflakes-their remarkable property, which is that each of the six arms grows outwards from a common center, and each grows independently, of its own internal rules. One arm cannot affect the others. And yet the arms are all alike. To me this is an embodiment of the pre-established harmony. Now, Daniel, in like manner, there grows out of the core of Natural Philosophy more than one system for understanding the Universe. They grow according to their own internal principles, and one does not affect another-as Newton and I demonstrated yesterday by utterly failing to agree on anything! But if it’s true-as I believe-that they are rooted in a common seed, then in the fullness of time they must adopt a like form, and become reflections of one another, as a snowflake’s arms.”

“I hope the poor snowflake does not melt before it reaches that perfection,” said Daniel, “in the heat of those fires that Caroline dreams of.”

“That is beyond our ability to predict or prevent. We can only do all in our power to move the work forward,” said Leibniz.