Provenance: Thomas Jefferson; by purchase to George Toole at the Dispersal Sale in 1827; by descent to Mrs. John Toole; by purchase to Henry Polkinhorn; by gift to William Wilson Corcoran; by purchase to an unidentified Washington dealer; by purchase to Mr. and Mrs. Parry Borgstrom; by gift of Ruth D. Borgstrom to the Thomas Jefferson Foundation in 1961
Accession Number: 1961-15
Historical Notes: In 1806 Jefferson ordered from the London firm W. & S. Jones "a 12. Inch Concave glass mirror in a plain black frame" costing £2-5.1 He had acquired a larger concave mirror in a more elaborate frame while living in France in the 1780s, for which this was probably a replacement.2
Jefferson intended using his concave mirrors, as well as the condensing lenses and scioptric ball he bought in London in 1786, with his microscopes.3 As he wrote in 1822, "in microscopic observations, the enlargement of the angle of vision may be more indulged, because auxiliary light may be concentrated on the object by concave mirrors."4 The reflecting mirror of a compound microscope would be placed at the focal point of the mirrors.
When a viewer stands outside the focal point of a concave mirror, his image is reflected upside down. This optical phenomenon may account for the mirror's location in the Entrance Hall in an inventory prepared shortly after Jefferson's death.5 It might have become a source of family entertainment in Jefferson's last years, when he had abandoned more complex scientific experiments.