The Chevalier de Borda developed this type of reflecting circle, and
published a description of it in Paris in 1787. This example has a silvered
scale that is graduated every 20 minutes and read by two verniers with tangent
screws and magnifiers to single minutes. It was made by Étienne
Lenoir (1744-1832), the French craftsman who is credited with having made Borda’s
first instrument of this sort. It belonged to Columbia College (now University)
in New York, and probably dates from the 1790s.
Ref: A. J. Turner, From Pleasure and Profit to Science and Security. Étienne
Lenoir and the transformation of precision instrument-making in France,
1760-1830 (Cambridge: Whipple Museum of the History of Science, 1989).
