"BORDA" TYPE REFLECTING CIRCLE
Circa 1850
Signed on the outer ring "Schwartz dit Lenoir a Paris (No. 120)". Six-spoke 10.75" diameter blackened brass frame. Outer brass ring with inset steel scale, divided 0-720 degrees. Blackened brass radius arm with clamp and tangent screws, fine adjuster and magnifier. Interior arc divided into two half arcs of 0-180 degrees. With screw locks, sighting mount, mirrors, filters and removable handle, along with additional lenses and filters. Within the original mahogany box with hinged lid and brass handle and latches. Interior of lid with a label for Otto Hess, Buenos Aires, Argentina, instrument vendor and calibrator. Marked on the exterior #473.
Box height 4". Width 12.75". Depth 12.75".
Provenance:
Historical Technology, Inc., Marblehead, Massachusetts, 1991.
The Kelton Collection of Marine Art & Artifacts.

Notes:
Jean-Charles de Borda (1733-1799) refined the reflecting circle by modifying the position of the telescopic sight in such a way that the mirror could be used to receive an image from either side relative to the scope, which simplified the use of the instrument. With the help of Etienne Lenoir, further refinements were incorporated to the instrument to its definitive form in 1777. This instrument was so distinctive it was given the name "Borda" circle.

Overall excellent condition, in need of minor cleaning and servicing.

The absence of a condition report does not imply an object is free of defects. All items may have normal signs of age and wear commensurate with their
age; these issues will likely not be mentioned in the condition report. Please contact Eldred's before the auction with any condition questions. Questions about condition will not be answered after purchase. Condition reports are provided as a courtesy, and we are not responsible for any errors or omissions. Important note on frames: Frames are not guaranteed to be in the same condition as they are in the item photograph. Due to handling and shipping, many frames, especially antique ones, are prone to losses. If you have questions about the condition of a frame, please contact us prior to the auction.