2026-10-06 Schadewald, The Plane Truth (cantab.net e-book), Parallax

URL: https://www.cantab.net/users/michael.behrend/ebooks/PlaneTruth/pages/Chapter_01.html (read about the first half; the page was truncated at 50,000 of about 94,600 characters). Other chapters found but not read: Ch.2 "Hampden and the Old Bedford Canal", Ch.3 "The Bedford Canal Swindle Detected and Exposed", Ch.4 "The Universal Zetetic Society", Ch.5 "Carpenter and the American Flat-Earth Movement", Ch.6, Ch.9, Appendix B, Notes (same folder, Chapter_02.html and so on). Status: secondary. Robert J. Schadewald was a critic of flat-Earth and creationist claims [memory: high], so his framing is that of a critic. He quotes primary newspapers and pamphlets at length, and those quotations are the useful part. Result: positive.

Findings that bear on the inventor's principles [web: URL above]

1. Manea Fen, 1838-39. Rowbotham was Secretary of the Cambridgeshire Community (an Owenite colony of William Hodson) on the east bank of the Old Bedford, just north of Welche's Dam. The canal runs straight for about 6 miles to Welney Bridge. Schadewald dates the first experiments to summer 1839 (Wikipedia says 1838). He says Rowbotham's later accounts of them are contradictory: one has him seated in the water with a telescope a few inches above the surface; the other has a surveyor's transit on a bridge and two flagged boats sent in opposite directions. Bearing on claim 2: the founding observation exists in at least two versions. The reviewers should compare them.
2. 1849 pamphlet (16 pp.). Six experiments with a theodolite. The example quoted is the "New Bedford" river: a boat 6 miles from the theodolite, no convexity detected, and "a fall of 24 feet" claimed for 6 miles (Schadewald ref. 1.17). The 1865 book instead gives the Old Bedford, a bather's eye 8 in above the water and a flag 3 ft high (facts.json). Schadewald also mentions an 1851 pamphlet, not yet identified.
3. RAS, 8 Dec 1848. The pamphlet's title page claims "a paper read before the Royal Astronomical Society". De Morgan (who was RAS Secretary at the time) wrote in A Budget of Paradoxes that no account of such a paper appears in the Notice for that month. He described himself reading a few of the lecturer's arguments at the close of the meeting "for your amusement" (ref. 1.18). This is De Morgan's own account, as a critic and an officer of the Society. The deciding record is the RAS minutes and MNRAS vol. 9 (Dec 1848).
4. Lecture record from 1849. Rowbotham lectured at the Trowbridge Mechanics' Institute from 15 Jan 1849 as "S. Goulden". Two correspondents in the Wiltshire Independent wrote about it, one favourable and one hostile (refs 1.14-1.15). By the end of 1849 he was using "Parallax". The Burnley lectures of 5 and 7 Dec 1849 were reported in the Blackburn Standard: he did not appear for the second lecture after a question about ship hulls (ref. 1.16). Favourable reviews appeared in the Liverpool Mercury (25 Jan 1850) and the Athlone Sentinel (21 May 1852). Historical record (priority 4): named newspapers and dates to pull.
5. Teign River challenge. Rowbotham reportedly walked out of an agreed repeat of a canal-marker experiment because the committee had set up the markers without him (ref. 1.19). This is Schadewald's account; the primary source is not yet seen.
6. Plymouth, 1864, in R. A. Proctor's words (a critic and science writer). From the beach only half the Eddystone lantern could be seen. Proctor puts this down to weaker refraction than usual (which normally reduces the dip by about one sixth), and says Rowbotham claimed the result for his side (ref. 1.20). The book itself (digest p.164-166) reports Plymouth Athenaeum committees in Oct 1864 finding the Eddystone entirely out of sight at 5 ft above the beach. So the inventor's own text and his critic agree that the lantern was partly or wholly hidden from low down, and differ on what that means.
7. The mirror test (Plymouth Hoe, 90-100 ft). Proctor computes that the image of the horizon would sit less than 0.03 in below the image of the eye-pupil at a viewing distance of about 10 in, too small for most eyes to see (ref. 1.21). Check [calc]: dip = sqrt(2h/R) = 3.09e-3 rad (10.6 arcmin) for h = 100 ft. At 10 in that is 0.031 in, or about 0.026 in with normal refraction. This bears directly on the book's Camera-house mirror test (claim 2; book pp.168-170, 110 ft, 25 Oct 1864).
8. Air-gun. Schadewald quotes the book: flight time averaging 16 s, the ball falling within a few inches, and twice back into the barrel. This agrees with the digest (8 s up, 8 s down).
9. Sources of the model. He names The Anti-Newtonian (1819, anonymous, 38 pp.), with a north-centred disc and ice wall, as almost certainly Rowbotham's source, although Rowbotham never cites it. He also names Thomas Reid's "Common Sense" realism and Baconian empiricism as the philosophical background of the zetetic method. Bearing on claims 1 and 6 (principles of the method).
10. Biography. Born in Didsbury Chapelry, Manchester, 1816. His mother's family, the Birleys, were cotton manufacturers. The Inquiry into the Cause of Natural Death ("Tryon", 1842; 2nd ed. 1845) gives the claim of 320 cases cured.

Not yet read in this source

• The rest of Ch.1 (the 1865-84 period, death) and Ch.2-4: the Hampden-Wallace affair, the Universal Zetetic Society, and the Blount 1904 photographs. Recheck first.