radius 9.25 inches
This octant has an ebony frame, reinforced brass index arm, and ivory name
plate. The ivory scale is graduated every 20 minutes from -3o to +100o
and read by vernier with tangent screw to single minutes of arc. There is also a
back sight and a back horizon glass that could be used to measure angles greater
than 90o. John William Norie established a Navigation Warehouse in
London in 1799. The firm traded as Norie & Co. from 1816-1839.
Ref: Gloria Clifton, Directory of British Scientific Instrument Makers
1550-1851 (London, 1895), p. 201.