This may be one of the earliest extant instruments of the United States Coast Survey.
Thomas Jones, who worked as an instrument maker and dealer in Liverpool during the period
1816-1831 should not be confused with the Thomas Jones of London who made the transit
theodolite for the Coast Survey, that is also in the collections.
The vertical circle attached to one end of the slightly conical horizontal axis is graduated
to 15 minutes, and read by opposite verniers to single minutes. There is a wooden lamp holder at
the other end of the axis. The lattice work cast iron base has 3 leveling feet.
Ref: Gloria Clifton, Directory of British Scientific Instrument Makers 1550-1851 (London,
1995), p. 154.