What device did Lewis Carroll invent for writing in the dark?

Lewis Carroll invented the nyctograph for writing in the dark.

Carroll devised the device in 1891 because he was often awakened at night by ideas and did not want to light a lamp, write normally, and then extinguish it. The nyctograph was a card template with square openings that guided his fingers while he marked symbols without relying on sight. He later transcribed the encoded notes in daylight.

Its symbols formed a compact substitute alphabet based on dots and strokes, with special signs for functions such as “and” and “the.” The final design used a row of 16 square spaces. Carroll first called the invention a “typhlograph,” but the name was changed to “nyctograph,” from Greek roots associated with night. It is sometimes confused with a noctograph, a different writing aid using carbon paper and a stylus. Carroll’s nyctograph was instead a tactile template paired with his own symbolic writing system.