The ogham is an ancient alphabet from Celtic culture. It seems to originate in the 4th century. It is a primitive alphabet with uses related to magic, testimonies and epitaphs on stone. The very form of this vocabulary is directly related to the technique and the material. Since you have to carve a stone, or at least a solid porous surface, you need a sharp tool to be able to express yourself. The orientation of the inscriptions seems varied, opening this alphabet towards a topology. We find vertical engravings on stones, and horizontal writings on paper. Going beyond its support, the ogham adapts to dimensions, axes, reading directions and their geometry.