Cipher methods Symbols
Nyctography (Lewis Carroll)
Nyctography (from Greek nyx, “night” + graphein, “to write”) is a writing system invented in 1891 by Charles Lutwidge Dodgson — better known by his pen-name Lewis Carroll — to let him capture his own ideas at night without lighting a candle or getting out of bed.
He described the procedure in the letter A Method of Taking Down Thoughts at Night published in The Lady magazine in 1891. Carroll suffered from insomnia and noted: “If I am awakened at night with a new idea, I must either forget it by morning, or strike a light to write it down — and then be wholly awake. Nyctography solves the dilemma.”
The nyctograph itself is a square frame perforated with a 4×4 grid of 16 holes guiding the hand in darkness: each cell holds a letter/digit composed of dots (one hole) and strokes (one hole + a neighbour) on a 2×2 grid.
How does nyctography work?
The cipher uses a monoalphabetic substitution: every letter of the plaintext is replaced by a glyph drawn from a fixed correspondence table. It is one of the oldest cryptographic techniques on record — already described in antiquity (Caesar cipher, ~50 BC) — and the most directly readable family for a beginner.
The table has 26 glyphs for the Latin letters + 10 glyphs for digits 0-9, i.e. 36 symbols in total. To encrypt, read the text character by character and replace each letter (and digit) with its glyph; to decrypt, consult the same table the other way around.
Cryptographic strength: weak. Because every plaintext letter always maps to the same glyph, the cipher falls to a frequency analysis in a few dozen words (in both English and French, E remains the most common letter, an immediate entry point). Monoalphabetic substitutions are therefore used today for their decorative, playful or pedagogical value — not to protect real information.
Historical and modern usage
- Carroll himself (1891-1898) — used his nyctograph in his bedside notebook for ideas that woke him up.
- Literary curiosity — nyctography appears in every Carroll biography as an example of his material ingenuity, alongside Mischmasch and his word puzzles.
- Historical accessibility tool — predates modern Braille’s broad adoption by about 50 years (Braille was invented in 1825 but standardised later) by proposing a tactile-visual fixed-grid alphabet.
Related variants
- Braille — tactile dot system (1825), 3 rows × 2 columns, predates nyctography but designed for the blind, not the dark.
- Pigpen — geometric grid alphabet (18th c.), same “case combinatorics” spirit.
- Nyctograph — the physical perforated object Carroll invented, distinct from the writing system it guides.
What are the weaknesses of nyctography?
- Monoalphabetic substitution — falls to frequency analysis.
- Public alphabet: reproduced in Carroll biographies and online glyph databases.
- Night thoughts: Carroll himself acknowledged that ideas noted at night often lost their clarity by morning, independent of the writing system.
The 26 letters
The 10 digits
