_____The surveying done, they turn to putting things on paper, including the map-making, which is Dixon's job. When he's done with that, "Mason eagerly rushes to inspect the Map of the Boundaries, almost instantly boggling, for there bold as a Pirate's Flag is an eight-pointed Star, surmounted by a Fleur-de-Lis," the symbol of, as Mason puts it, "England's most inveterately hated Rival ... France." But Dixon explains that "A Surveyor's North-Point, ... by long Tradition, is his own, which he may draw, and embellish, in any way he pleases, so it point where North by." This is his own, "his Hall-Mark," "an ancient Shape." Mason is concerned that "some, finding it upon a new Map, might also take it as a reassertion of French claims to Ohio." And though they bicker as usual for a while,
Mason is able to inspect the long Map, fragrant, elegantly cartouch'd with Indians and Instruments, at last. Ev'ry place they ran it, ev'ry House pass'd by, Road cross'd, the Ridge-lines and Creeks, Forests and Glades, Water ev'rywhere, and the Dragon nearly visible.... "This is beauteous Work. Emerson was right, Jeremiah. You were flying all the time."
But they still have some survey work to do in "the cheerless Bogs of Delaware," which takes them almost another year. Zhang still hangs around complaining about sha. And at one point Dixon reflects on what all their travels together have in common: "Slaves. Ev'ry day at the Cape, we lived with Slavery in our faces, -- more of it at St. Helena, -- and now here we are again, in another Colony, this time having drawn them a Line between their Slave-Keepers, and their Wage-Payers, as if doom'd to re-encounter thro' the World this public secret, this shameful Core."
At the end of June, when they finish their measuring, they go south to Baltimore, "and the moment when Dixon will accost the Slave-Driver in the Street, and originate the family story whose material Focus, for years among the bric-a-brac in Hull, will be the Driver's Lash, that Uncle Jeremiah took away from the Scoundrel." It is an act that earns Mason's often-withheld admiration. And it brings into focus another theme of the novel:
Having acknowledg'd at the Warpath the Justice of the Indians' Desires, after the two deaths, Mason and Dixon understand as well that the Line is exactly what Capt. Zhang and a number of others have been styling it all along -- a conduit for Evil.One night, as he is walking along the Visto, Mason sees Rebekah's ghost, urging him to "come back to our Vale.... You must leave Mr. Dixon to his Fate, and attend your own.... You ... must go back inside the House of your Duty. When you come out again, he will no longer be there, and the Dark will be falling." On Sept. 11, 1768, they sail for England.
There follows a fantasy about Mason and Dixon journeying together, westward beyond the Ohio. "Betwixt themselves, neither feels British enough anymore, nor quite American, for either Side of the Ocean. They are content to reside like Ferrymen or Bridge-keepers, ever in a Ubiquity of Flow, before a ceaseless Spectacle of Transition."
But in fact, they return to England and a meeting of the Royal Society Council in December 1768. The next transit of Venus is ahead, and the records of the meeting show that Dixon says he's "willing to go to the North Cape or Cherry Island; Mr Mason rather declined going; but added, that if he was wanted, he should be ready to go." As they leave the meeting, they are pursued by "Some horrible Boswell," who points out, "neither of you has been voted to membership in the Royal Society. Mr. Mason, we've heard you're the one here who's unhappy with that, whilst Mr. Dixon takes the more philosophickal View." Dixon replies, "Only the long view, Lad."
The truth is that Mason is feeling guilty about leaving his family, and especially about his father's criticism. "So he declines the North Cape, and another posting together, symmetrically as ever, to that end of the world lying opposite their first end of the World. 'Someone must break this damn'd Symmetry,' Mason mutters." He goes to observe the transit in South Ulster instead, but sees only "the ingress of Venus upon the Disk of the Sun, but not her departure." Ireland reminds him of America, "frontier Country," and he has a bad dream of Rebekah.
He returns with his report to Maskelyne, who annoys him with the alterations he has made to the office that used to belong to Mason's patron, Bradley, and his flaunting of his relationship to Clive of India. Maskelyne is also suspected of having used his position as Royal Astronomer to have his method of measuring longitude accepted over the more accurate method using John Harrison's chronometer. Cherrycoke comments to his audience, however, that Maskelyne "did what he could to support Mason's claim to Prize money from the Board of Longitude for his Refinements to Mayer's Lunar Tables, whilst seeking none for himself." In the end, Mason accepts a commission from Maskelyne to go to Scotland, and to visit Dixon along the way.