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 +109o, and read by vernier with tangent screw to single minutes of arc. The Smithsonian purchased this piece in 1903. At that time, it had a wooden box with a trade label that read "William Desilva, 78 Regent Road opposite the Bramley-Moore Hotel, Liverpool." Desilva was in business from 1851 to 1881, offering optical and nautical instruments.
Ref: Gloria Clifton, Directory of British Scientific Instrument Makers
1550-1851 (London, 1995), p. 83.
