Night writing

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Night writing was a system of code that used symbols of twelve dots arranged as two columns of six dots embossed on a square of cardboard. It was designed by Charles Barbier in response to Napoleon's demand for a code that soldiers could use to communicate silently and without light at night. Called sonography, each grid of dots stands for a character or phoneme.

Barbier's system was related to the Polybius square, in which a two-digit code represents a character. In Barbier's variant, a 6x6 matrix includes most of the characters of the French alphabet, as well as several digraphs and trigraphs:

A character (or digraph or trigraph) was represented by two axies of dots, in which the first column had one to six dots denoting the row in the matrix, and the second had one to six dots denoting the column: e. g. 4–2 for "t" represented by

As many as twelve dots (two columns of 6) would be needed to represent one symbol.

Barbier's system was found to be too difficult for soldiers to learn, and was rejected by the military; in 1821 Barbier visited the National Institute for the Blind in Paris, France, where he met Louis Braille. Braille identified the major failing of the code, which was that the human finger could not encompass the whole symbol without moving, and so could not move rapidly from one symbol to another. His modification was to use a 6 dot cell — the Braille system — which revolutionized written communication for the visually impaired.

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