title: Speculations on the possible causes of the Whymper apparition.
abstract: During the first ascent of the Matterhorn, a remarkable optical effect comprising three crosses surrounded by a great arch was observed by Edward Whymper, the British mountaineer. The authors review previous published explanations of the apparition. There are no photographs, only a woodcut and sketch, so the size of the apparition is not known, and it is not possible to make a definitive conclusion about what caused it. A fogbow and ice crystal arcs could have produced a circle and crosses in a direction consistent with the apparition. Some simulations are presented; one has a form approximating Whymper's sketch. However, while this simulation used a crystal type that can occur, it required an unusual alignment that would be very rare.
authors.affiliation: john.hardwick@culham.com
authors.forename: Cedric John
authors.initials: CJ
authors.lastname: Hardwick
authors.forename: Jason C
authors.initials: JC
authors.lastname: Knievel