Night writing was a system of code that used symbols of twelve dots (2 wide and 6 high) 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 letter or phoneme. Barbier's system was too complex for soldiers to learn, and was rejected by the military; in 1821 he visited the National Institute for the Blind in Paris, France, where he met Louis Braille. Louis 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 blind.