So on the liability side of Jones’s account, to illiteracy could be added a mysterious, probably criminal past, and a want of ambition. He had, however, one asset that was not possessed by the officer who was walking next to him up Lombard Street: he was a white-skinned Englishman. From time to time Jones was called upon to make the most of this asset by dressing up in a pair of breeches, leather shoes, a waistcoat, a long watch coat of a somewhat nautical cut, and a very plain horsehair periwig. This was the sort of get-up that a ship’s officer might keep stuffed in a footlocker while crossing an ocean, and pull out after dropping anchor in some harbor, so that he could go ashore and look minimally decent in the eyes of money-scriveners, victuallers, ship-chandlers, and insurance underwriters.

If these two were to hail a hackney coach and travel a couple of miles west to the new streets round Piccadilly and St. James, where shopping rather than shipping was the order of the day, their roles, in the eyes of most casual strollers, might be reversed. For people with an eye for clothes would notice that Dappa’s actually fit him, that they were of recent make, well cared for, and cleverly picked out. The lace around his shirt-cuffs had never been dragged through beer-foam, goose-grease and damp ink; his shoes shone like wax fruit. The sophisticated toffs of the West End would then take in the fact that Dappa was older, that he was alert to everything going on around them, and that when they came to street-corners Dappa went where he would, and Jones followed. Jones looked about himself curiously, but he was not really paying attention in the way that Dappa was. A West Ender, watching this procession of two stride past, might conclude that Dappa was a Moorish diplomat from Algiers or Rabat, and Jones his local guide.

But this was not the West End. This was the City of London. They were only a stone’s throw from Change Alley. No one paid much heed to clothing here, unless it was as a truly vulgar and shocking exhibit of wealth. By that standard both Dappa and Jones were invisible. Dappa, darting ahead through the crowd of money-men, was assumed to be the servant-a meat souvenir picked up on a trading-voyage-beating a path through the jungle, as it were, and keeping a shrewd eye for hazards. Jones, strolling in Dappa’s wake, was obviously the master, and what might in other settings have been seen as a stupid or vacuous expression could be taken, here, as the meditative phizz of a financial savant who was trying to plumb the meaning of the latest trend in Sword Blade Company share prices, and couldn’t be bothered to dress himself elegantly or indeed to find his own way down the street. His absent-minded way of taking in everything around him was proof that his was a mind tuned to follow the divagating strains, and quiver in sympathy with the startling chords, of the Market.

Or so Dappa told himself, to check his own impatience, when Seaman Jones paused to chat up a pretty orange-girl on a street-corner, or reached out to accept a handbill from a dirty, bawling pamphleteer. When they came at last to the doorway of Worth’s Coffee-House on Birchin Lane, just across the way from the Heraclitean riot of Change Alley, Dappa fell to the rear. Jones strode forward and entered the coffee-house first. A few moments later Dappa was pulling Jones’s chair out for him as he seated himself at a vacant table, and scurrying after a maid to make Mr. Jones’s desires known.

“We are early,” Dappa told Jones after he had got back to the table with the coffee, “and Mr. Sawyer is ever late, and so make yourself comfortable, as I cannot. After this, there’s no more leisure until we reach Massachusetts.” And Dappa took up the pose of a servant, standing behind Jones, ready to dart forward and tend to emergent needs.

Everyone else in the place was either involved in a conversation or, if alone, reading something. Worth’s Coffee-House was the haunt of a sub-species of petty financier who provided bridge loans, and other, less easily explained financial instruments, to the shipping trade. Of the singletons scattered about the place, some were salts consulting tide-tables or almanacks. Others looked like money-scriveners or money-goldsmiths. Their choices in reading material leaned towards London newspapers. Jones, here, was the odd man out in that he could not read at all. But at the corner of Gracechurch and Lombard, he had accepted a libel from a nasty tub-faced tout who looked and smelled as if he’d washed his face with rancid tallow, and who had bestowed an evil look on Dappa as he’d walked by. Jones had rolled it up and carried it here in one hand, looking for all the world like a man of affairs toting a Bill of Exchange to be redeemed. But now, in an effort to blend in with this literate crowd, Jones unrolled the handbill and smoothed it out on the table, and bent over it, aping the poses of the readers around him.

He had it upside down! Dappa bent his face toward the floor, and stepped forward so that he could discreetly knee Jones in the arse. But Jones was quicker than Dappa gave him credit for. Though he knew nothing of letters, he had figured out on his own that the document needed to be spun around. For this bill was illustrated: at the top of the page was a fist-sized blot of ink, a butcherous woodcut of a savage black-skinned man with spraying dreadlocks. His throat was clasped in a white lace cravat, his shoulders dignified by good English tailoring. Printed beneath this portrait in crusty letters an inch high was the word

followed by

A SLAVE, property of MR. CHARLES WHITE, ESQ., is missing and presumed stolen or astray. A REWARD in the amount of TEN GUINEAS shall be given to the first party who brings this Neeger to the dwelling of Mr. White on St. James’s Square.

And then finer print, which Dappa would need glasses to read. But he could not get his glasses out of his breast pocket, because not a muscle in his body would move.

HE WISHED HOOKE WERE HERE. A Natural Philosopher could not but be enthralled by all that was laid out for view by such a rare low tide. The sun had sunk low in the west and, behind London’s dome of smoke, shone the color of a horseshoe when the farrier beats it out on the anvil. That light was skidding across the tidal flats all round, making them seem not so flat at all. The surface of the muck was rippled, as if it were a pond that had been disturbed by a chill wind, then frozen. But more remarkable to Daniel was the shape of Foulness Sand, a few miles to the north, across the mouth of the Thames. This country of muck, larger than some German principalities, lay concealed beneath the water most of the time. It was devoid of any features such as rocks or vegetation. Yet when the tide drew off, the great quantity of water that had been stranded in the dells of all those frozen ripples drained away, not as a streaming sheet, and not by quiet seepage into the earth, but by finding its way to the low places. One hand-sized puddle would erupt in upon its neighbor, and those two would join forces and go looking for a nearby place that lay a hair’s breadth lower, even as every other dollop of water for miles around was pursuing a like strategy. The result, integrated (to use Leibniz’s terminology) over the whole of Foulness Sand, was that entire systems of rivers and tributaries sprang into being. Some of those rivers looked as old as the Thames, and big enough to build cities on; yet in a few hours they’d disappear. Existing in a state of pure alienation, unsoftened by reeds or willows, and not encrusted by the buildings of men, they were pure geometry. Albeit geometry of an irregular and organic cast, repugnant to Euclid or, Daniel suspected, to the silver-haired knight who was standing next to him. But Hooke would have seen beauty and found fascination there, and wrought pictures of it, as he had done with flies and fleas.