Ring of the Fisherman Ring of the Fisherman The Ring of the Fisherman (Latin: "Annulus Piscatoris"; Italian: "Anello Piscatorio"), also known as the Piscatory Ring, is an official part of the regalia worn by the Pope, who is head of the Catholic Church and successor of Saint Peter who was a fisherman by trade. It used to feature a bas-relief of Peter fishing from a boat, a symbolism derived from the tradition that the apostles were "fishers of men" (Mark 1:17). The Fisherman's Ring is a signet used until 1842 to seal official documents signed by the Pope. A letter written by Pope Clement
Projective line over a ring a Clifford algebra. The ring of dual numbers "D" gave Josef Grünwald opportunity to exhibit P("D") in 1906. Corrado Segre (1912) continued the development with that ring. Arthur Conway, one of the early adopters of relativity via biquaternion transformations, considered the quaternion-multiplicative-inverse transformation in his 1911 relativity study. In 1947 some elements of inversive quaternion geometry were described by P.G. Gormley in his paper "Stereographic projection and the linear fractional group of transformations of quaternions". In 1968 Isaak Yaglom's "Complex Numbers in Geometry" appeared in English, translated from Russian. There he uses P("D") to describe line geometry in the Euclidean