In fact, he is said to have discovered the already existing language by total accident; having ducked into a nearby house to escape the rain, he fell upon a pair of deaf twin sisters and was struck by the richness and complexity of the language that they used to communicate among themselves and the deaf Parisian community.[citation needed] The abbé set himself to learning the language, now known as Old French Sign Language, and eventually he established a free school for the deaf. At this school, he developed a system he called "methodical signs", to teach his students how to read and write. The abbé was eventually able to make public demonstrations (1771–1774) of his system, demonstrations that attracted educators and celebrities from all over the continent and that popularised the idea that the deaf could be educated, especially by gesture.