LINN

lunar crater the reported disappearance of which in the 19th century caused scientific controversy and stimulated study of the Moon. In 1866 Julius Schmidt, director of the Athens Observatory, announced that the crater, formerly easily seen, was gone, and only a white spot was visible where it had been. Schmidt and other skilled observers had until 1843 agreed that Linn (named for the Swedish botanist Carolus Linnaeus) was a deep crater about 10 kilometres (6 miles) in diameter. Apparently, no careful observations were made of the site between 1843 and 1866. In 1903, however, there came to light a drawing made in 1788 in which Linn was also shown as a white spot; this cast doubt on the reality of the reported change. Modern observations show a crater about 1.6 kilometres (1 mile) wide, near the centre of a light-coloured mound at about 28 north, 12 east. The appearance of the formation varies considerably with the angle of sunlight. Whether any structural change or occasional obscuring emission of gas has occurred is uncertain.