Vulcan (Hypothetical planet)

found: Work cat.: Abraham, K. Moon veils Vulcan, and the sun veils Neptune, 1989.

found: De Vore, N. Encyc. of astrology, 1976:Vulcan (an hypothetical planet, much conjectured among ancient astrologers, the orbit of which is supposed to lie inside that of Mercury. Astronomers have so far found no justification.)

found: Facts on File dict. of astron., 2000(Vulcan: hypothetical major planet thought during the 19th century to orbit the Sun within the orbit of Mercury. Searches for it during total solar eclipses and at suggested times of transit across the Sun were all unsuccessful. It is now known not to exist.)

found: McGraw-Hill dict. sci. tech.(Vulcan: hypothetical planet that was supposed to have an orbit within the orbit of Mercury; its existence was considered about 1859, and in the next few years but it is generally considered by present-day astronomers to be non-existent.)