Two years later, a second commission takes Mason and Dixon to America to produce the famous Line, a 244-mile boundary between Pennsylvania and Maryland that eventually divided South from North, Slave from Free. This second section of the novel is by far its longest, and almost wholly without narrative tension. Mason and Dixon survey a stretch of border, bicker, meet a robot duck, a French chef, a Chinese Feng Shui master (in flight from the Jesuits), a giant Eel, a giant Golem, a giant Worm (like the giant Adenoid in Gravity's Rainbow, or the giant, lab-stomping Saurian in Vineland) - and so on.
Four years into the expedition, Indian opposition halts the Line 36 miles short of its intended terminus. So back the party goes to Philadelphia, a no-less laid-back progress that involves yet more symbolic encounters, such as those with Stig the Swedish irredentist or Zepho Beck the "Were- beaver," a victim of kastoranthropy.
The novel ends with a brief, redemptive coda or "Last Transit". Mason and Dixon return to England and re-establish ties with parents and children. Before Dixon dies he and Mason express a new and affecting tenderness, "sit for a while in what might be an Embrace". Though they have spent their lives "in the service of a Flag whose Colors we never saw", feeding through their skill a rapacious and amoral system based on division, distinction, demarcation, they are to be pitied, even admired. The mellow good-heartedness of Vineland - too soft for fastidious postmodernists - lives on, for all the rigour and ingenuity of the attack on reason, authority, commerce.
This attack draws deeply on Pynchon's fascination with science and technology, which allies Mason and Dixon with V and Gravity's Rainbow. In place of quantum mechanics and rocket science we get astronomy and land surveying. There is much talk of precession, refraction, triangulation, parallaxes. The metaphoric properties of astronomy, cartography and topography are artfully interwoven, as are associated historical figures. Several extended jokes depend on dizzying horological conundrums, as when two clocks converse or a watch bites a thief's finger.
Then there's the massed research. Pynchon is reputed to have taken a quarter-century to write this book much of it, it is now clear, spent hunched over other books. Inkhorn terms abound: ort, ovine, annulis, trebuchet, macaronickal, riparian. The most fantastical details are rooted in fact. Jenkins's flirtatious Ear appears because Pynchon knows Robert Jenkins was appointed Governor of St Helena in 1741. The robot duck who first attacks and then falls for Armand Allegre, the French chef (victimised by the fame of his duck dishes, "those old canards"), is also historical, the creation of Jacques de Vaucanson (1709-1782), a scientist hailed by Voltaire as a modern Prometheus (a title Mary Shelley borrowed for Frankenstein).
As for the Feng Shui master and his Jesuit pursuers, they too derive from history. It was the Jesuits who introduced China to Western astronomy, cartography, clockwork and other exotica. Feng Shui, which means harmony between man and nature, was the ideology of their antimodernising enemies. So it makes sense for Captain Zhang, the Feng Shui master, not only to describe the Mason-Dixon Line as "a Conduit for what we call Sha, or, as they say in Spanish California, Bad Energy," but to be pursued by Father Zarpazo, the Wolf of Jesus, who wants him returned to captivity in a Jesuit monastery in Quebec.
The Line, and the system that spawned it, violates nature as well as man. "Ev'rywhere else on earth," explains Captain Zhang, "Boundaries follow Nature - coast-lines, ridgetops, river-banks - so honoring the Dragon or Shan within, from which Land-Scape ever takes its form. To mark a right Line upon the Earth is to inflict upon the Dragon's very Flesh, a sword- slash, a long, perfect scar." This helps explain the dragon-like creatures (giant Eel, giant worm) haunting the story and threatening the characters' sanity.
Dixon describes his fear of open spaces ("Rum affliction for a Surveyor," comments Mason), in terms that recall these creatures, "as an incentive, to enclose that which had hitherto been without form, and hence haunted by anything and ev'rything". Before meeting Mason, Dixon has enclosed the fields of Co Durham (driving small farmers and labourers off the land), a process whose social costs in the name of modernisation and reason are clear.
Yet Dixon is brave as well as fearful, and he hates slavery. In one of the best scenes, Mason prevaricates as Dixon rounds on a Virginia slaver and threatens to kill him. "No! Please," the slaver wails, "My little ones! O Tiffany! Jason!" The jokey deflation is characteristic, marking even the slaver as a hapless cog. There are no real villains in the novel, only dupes and pawns. Oppression flows from shadowy, impersonal agencies: the Royal Society, the East India Company, the Masons, the Jesuits, the Castle, the Desk. Nor is God much of a presence. Though Mason, a Deist, thinks of his astronomical measurements as "steps of an unarguable approach to God, a growing clarity", he's as much in the dark by the novel's end as Dixon.
The story is narrated after the fact, in 1786, by the American expedition's chaplain, the Rev Wicks Cherrycoke (other good made-up names include Lud Oafery, Don Foppo de Pin-Heado and the frigate HMS Unreflective) and its idiom is 18th-century pastiche. There is much flourishing of capitals and contractions, as well as antique spelling; but also dozens of comic anachronisms ("multiplex," "Proclamation-Shmocklamation").
Anachronism, or seeming anachronism, figures also in more extended jokes, as when the real-life 18th-century Jesuit astronomer Father Lemaire cooks pizza, or a Chinese astronomer in the reign of one of the Hia Emperors goes hang-gliding, or George Washington's black-Jewish slave Gershom does stand-up. That many of these moments are not only funny but thematically relevant, like the "comic relief" in Shakespeare, is typical of the novel's exhausting brilliance. Readers with stamina will be amply rewarded.