Interactive exhibit: a vellum folio carrying a thirteenth-century Latin Book of Hours written over an erased fifth-century Greek mathematical treatise. Moving the wavelength slider from visible light to ultraviolet makes the erased Greek text and its spiral diagram fluoresce into legibility; moving it to infrared deepens the Latin ink and reveals the parchment’s follicles, veining and scrape marks.
Manuscript recovery · multispectral imaging · Genève
Two books share this page. Only one was meant to survive.
Under the lamp: a Book of Hours copied about 1240 — over a fifth-century Greek treatise on spiral equilibrium that a scribe scraped away to reuse the skin. Iron-gall ink bites deeper than any knife can reach. Drag the wavelength to 365 nm and the erased mathematics fluoresces back.
- λ
- 550nm
- band
- VISIBLE · reflectance
- source
- LED bank 06/12 · 550 nm ±10
- barrier
- —
- exposure
- 1/8 s · f/5.6 · 12 frames
- undertext legibility
- 04%
Drag the spectrum under the folio — or focus it and use ← → (PgUp/PgDn hops band to band). The slider is the lamp.
§ case files
Six texts that came back.
Recovery is counted in characters read to consensus by two independent editors — never in hope. Shelf marks are ours; former homes are given as olim.
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PL MS 7olim Tolosa 887on the benchover — Horae B.M.V., Latin, s. XIII² Herakleides of Kyzikos, On the Equilibrium of Spirals — Greek, s. V91%
The only witness to Hellenistic spiral quadrature outside Archimedes.
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PL MS 19olim Wien, priv.over — Cistercian account roll, Latin, s. XIV Ptolemaic star tables with scholia — Greek, s. IX83%
Every position silently recomputed for the meridian of Baghdad.
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PL MS 12olim Sinai, N.F.over — Georgian hymnal, s. X Galen, On Simple Drugs, Syriac version of Sergius — s. VI78%
Carries the pharmacology chapter missing from every Greek copy.
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PL MS 3olim Bobbioover — Priscian, Institutiones, Carolingian minuscule, s. IX Gothic Bible, Epistle to the Romans — s. VI64%
Adds forty-one verses to the entire surviving Gothic language.
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PL MS 22olim Nonantolaover — Rule of St Benedict, Latin, s. XII Latin comedy, author unknown, iambic senarii — s. IV41%
Eleven complete verses of a play with no surviving title.
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PL MS 31acq. 2025capture 6/12over — Notarial formulary, Latin, s. XV Unidentified — Greek musical notation suspected12%
Six bands captured; the neumes brighten at 505 nm, which is odd.
§ the bench
ORPHEUS-12.
One lamp is a liar. Twelve narrow bands, two raking arms and a barrier filter tell the truth slowly — about forty minutes a folio. Named for the only imaging protocol older than ours: look back carefully, and you may keep what you love.
| sensor | 151 MP achromatic CMOS, 14-bit, Peltier-cooled |
|---|---|
| illumination | 12 narrowband LED banks, 365–940 nm, ±10 nm |
| fluorescence | UV-A excitation 365 nm · long-pass 420 nm barrier |
| raking | 2 arms at 10°, E/W — reads erasure by shadow |
| registration | sub-pixel, σ ≤ 0.22 px across the 15-frame stack |
| separation | PCA + MNF; pseudocolour keyed per scribal hand |
| throughput | ≈ 40 min per folio · 12 bands + 2 raking + 1 transmissive |
| dose | ≤ 2.1 klx·h per campaign — under one gallery-day of light |
- Collate & cradle — folio mapped, lacunae logged, spine angle fixed at 104°.
- Capture — twelve bands, two raking passes, one transmissive.
- Register — every frame warped to the 550 nm reference.
- Separate — principal components pull ink from ink, hand from hand.
- Edit — two editors read blind; only agreement counts as recovered.
Select a band to retune the lamp on the folio above.
§ essay
What the Knife Leaves.
A monastery kitchen ledger will tell you what a book cost before it was a book: sixty-eight sheep for one lectern Bible, dressed and limed and scraped thin through a Burgundian winter.1 Parchment was land, weather and labour pressed flat enough to write on. When the words on a skin stopped earning their keep — the liturgy reformed, the language died, the mathematics went out of fashion — the skin was still worth a flock. So the knife came out, and the pumice after it, and the page went back to being a field.
The scribe who erased the treatise now on our bench did nothing shameful by his own lights. He was recycling. But iron-gall ink is not a coating; it is a provoked chemistry — oak-gall tannin set against green vitriol — and it does not rest on parchment so much as bite into it, forty to eighty microns down into the collagen weave.2 A knife can take the body of a letter. It cannot reach the grave.
Ultraviolet is how we read the grave. At 365 nanometres, parchment fluoresces: the skin answers invisible light with a pale blue-white of its own making. Where old ink once etched the collagen, the answer fails — fluorescence is quenched, and the dead letters print themselves as shadows on the glow.3 Note what this means. We never photograph the erased ink; there is no ink left to photograph. We photograph the skin’s memory of being written on. The text survives the way a scar survives.
ὅπερ ἔδει δεῖξαι.
It is tempting to resent the prayer book for standing on the mathematics. That has it backwards. The Hours are why this vellum stayed bound, dry, shelved and wanted for eight centuries; erasure was the rent the treatise paid for shelter. Nearly every great recovered undertext survives by the same unhappy bargain — the Method of Archimedes lived inside a prayer book for seven hundred years precisely because somebody kept valuing the prayers.4 The eraser and the author are co-donors to the archive. Only one of them meant to be.
So the laboratory does not take sides. We will not lift the Hours to reach the Greek, and we will not pretend the Greek is not there. The folio leaves the bench exactly as it arrived — one skin, two voices, eight centuries apart — except that now both can be heard at once, each in its own light. What the knife left, the lamp returns.