Double sounding sextant.
Double sounding sextant with anodized brass circle-pattern frame and polished brass limb with wooden handle in fitted mahogany box containing in the lid a trade label for J.D. Potter, 31 Poultry London, invented by Rear Admiral Frederick Beechey and made by Nathaniel Worthington, London, 1845-1851. Fitted with two parallel inlaid silver scales marked; (lower) -2° from left to155° with 20 arc-min. divisions to 129° and (upper) -10° at right to147° with same to 126°; each with silver vernier scale divided to 20 arc-min.; four index shades (3 red, 1 green), no horizon shades; two index glasses; upper magnifier (single lens) on a 55 mm swivelling arm and lower one on a bar and bracket for telescope (62 mm, large objective) erect image (other telescope missing) with perpendicular adjustment. Accessories include magnifying glass; adjusting key; adjusting pin.
Details
- Category:
- Surveying
- Object Number:
- 1876-990
- Materials:
- brass (copper, zinc alloy), glass, steel (metal), mahogany (wood), felt and paper (fibre product)
- Measurements:
-
overall: 170 mm x 295 mm x 300 mm, 4.265kg
- type:
- sounding sextant and double sextant
- credit:
- Admiralty Hydrographic Department