This unusual instrument consists of a brass circle (the rim of which is graduated to 30 minutes and read by vernier to single minutes), with a movable telescope above, and a fixed one below. The signature could refer to George Adams, Sr. (fl.1734-1772) or to his son, George Adams, Jr. (fl. 1772-1796), both
prominent instrument makers and dealers in London. The French mathematical instrument maker, Nicholas Bion, described a similar instrument, terming it a "planchette ronde." The English translation of Bion’s text termed it a "theodolite." The donor, a direct of Andrew Ellicott, thought that Ellicott might have used this instrument, but we have yet to find any confirming evidence.
Ref: N. Bion, The Construction and Principal Uses of Mathematical Instruments, English translation by Edmund Stone (London, 1758), pp. 106-108 and plate XII.
Gloria Clifton, Directory of British Scientific Instrument Makers 1550-1851 (London, 1995), pp. 2-3.
