A noctograph is a writing instrument composed of a chemically treated paper

Paper

Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

, over which is placed a metal grid. The user writes with a metal stylus. The original purpose was to allow the blind

Blindness

Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

 or partially sighted to write with more ease than with a traditional pen

Pen

A pen is a device used to apply ink to a surface, usually paper, for writing or drawing. Historically, reed pens, quill pens, and dip pens were used, with a nib of some sort to be dipped in the ink. Ruling pens allow precise adjustment of line width, and still find a few specialized uses, but...

, although it has also been used by the fully sighted to write in the dark

Dark

Dark commonly refers to darkness, the absence of light.Dark may also refer to:*Evil, sinister or malign*Dark , a term used to describe a broadcasting service that has ceased transmission...

. It was originally patented by Wedgewood of London in 1806.