Among the first people to recognize that Bishop's ring was a result of the diffraction of sunlight by dust particles was the Swiss physicist Eduard Hagenbach-Bischoff. See: François-Alphonse Forel (1884) "La couronne solaire de l'été de 1884" (The solar corona of the summer of 1884), Archives des sciences physiques et naturelles, series 3, vol. 12, pages 173–184; see especially page 182, where Forel says that the corona was not consistent with a 22° halo, which is produced by refractions through ice crystals.
