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Micrometer with case and cover. Thomas Jefferson Foundation, Inc.Artist/Maker: Alexis Marie Rochon (1741-1817)[1]

Created: c. 1780

Origin/Purchase: France

Materials: brass, glass; case: pressed board, papers; cover: textile, leather

Dimensions: L: 35.6 (14 in.) closed; 48.3 (19 in.) extended; case: L: 35.6 (14 in.); D: 5.2 (2 1/16 on.); cover: 36.8 x 41.9 (14 1/2 x 16 1/2 in.)

Location: Storage

Provenance: John Hartwell Cocke; by descent to John Page Elliott; by gift and purchase to the Thomas Jefferson Foundation in 1992

Accession Number: 1992-4-2

Historical Notes: Jefferson's list of "Mathematical Apparatus" includes "a telescope of Iceland chrystal by the abbè Rochon & Herbage."[2] This "lunette" as he sometimes called it, combined an achromatic telescope with a prismatic micrometer, based on the use of double-refracting rock crystal.

Jefferson was in Paris while the Abbè Rochon was making his important new discoveries in optics at La Muette, the royal Cabinet de Physique in Passy. At Benjamin Franklin's house nearby, he had seen Rochon demonstrate his micrometer and had learned tis principles from the inventor himself. "I was intimate with him France," Jefferson wrote in 1812, adding that he possessed "one of his lunettes, which he had given to Doctor Franklin and which came to me thro' Mr. [Francis] Hopkinson."[3] Later he lamented that Rochon's micrometer had not been widely adopted in navigation and land armaments, commenting that "it is one of the remarkable proofs of the slowth with which improvements in the arts and sciences advance."[4]

John Hartwell Cocke's known interest in Jefferson's scientific instruments suggests the possibility that Cocke acquired this micrometer from Jefferson's estate after his death.


  1. This article is based on Stein, Worlds, 352.
  2. List of "Mathematical Apparatus, in Bedini, Statesman of Science, 501. Manuscript available online from the Massachusetts Historical Society.
  3. Thomas Jefferson to Robert Patterson, Monticello, December 27, 1812. Thomas Jefferson Papers. Library of Congress. Polygraphy copy available online.
  4. Jefferson to Abbè Rochon, December 14, 1813. Colonial Williamsburg.


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