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Surveying compass
Surveying compass
Bowl: Brass, dry, marked with 4 cardinal points and on verge quadrantally in degrees. Glazed, Brass cover. Has vernier on outside. Bowl, arc and telescope all move in unison in azimuth, operated by screw on underside, operated by screw on underside compass platform.
Needle: Very elongated diamond with brass weight on one arm. Has jewelled pivot cap at centre. Length. 5" (12.7cm).
Pivot: Steel spike set in brass mount.
Telescope: Brass, clamped to arc by two hinged brackets. Has focusing knob on front. O.G. and eyepiece both have dust covers. Length 15" (38.2cm).
Arc: Cogged brass arc graduated to 180 degrees quadrantally. Has Y shaped radial arm connecting to telescope. Arm has two adjuster screws that operate on cogs, one to move the arm. Spirit level attached to diameter of arc. Arc attached to compass platform and spans compass. Diameter 8.25" (21.0cm)
Compass platform: Circular with two arms, one arm holds spirit level. Circle is graduated quadrantally in degrees. Has attachment for tripod. O.A. Height 12.25" (31.2cm)
Bowl: Brass, dry, marked with 4 cardinal points and on verge quadrantally in degrees. Glazed, Brass cover. Has vernier on outside. Bowl, arc and telescope all move in unison in azimuth, operated by screw on underside, operated by screw on underside compass platform.
Needle: Very elongated diamond with brass weight on one arm. Has jewelled pivot cap at centre. Length. 5" (12.7cm).
Pivot: Steel spike set in brass mount.
Telescope: Brass, clamped to arc by two hinged brackets. Has focusing knob on front. O.G. and eyepiece both have dust covers. Length 15" (38.2cm).
Arc: Cogged brass arc graduated to 180 degrees quadrantally. Has Y shaped radial arm connecting to telescope. Arm has two adjuster screws that operate on cogs, one to move the arm. Spirit level attached to diameter of arc. Arc attached to compass platform and spans compass. Diameter 8.25" (21.0cm)
Compass platform: Circular with two arms, one arm holds spirit level. Circle is graduated quadrantally in degrees. Has attachment for tripod. O.A. Height 12.25" (31.2cm)
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Object Details
| ID: | ACO0103 |
|---|---|
| Type: | Surveying compass |
| Display location: | Not on display |
| Creator: | Joseph, J. G. |
| Date made: | circa 1810 |
| Credit: | National Maritime Museum, Greenwich, London, Admiralty Compass Observatory |
| Measurements: | Overall: 302 mm x 360 mm x 185 mm |
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