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Zigzag compass
A zigzag compass received from the Board of Invention and Research.
Bowl-This is a pattern 14 Thomson compass bowl in the base of which a clockwork mechanism has been fitted. This mechanism drives a second lubber line backwards and forwards across the true lubber. By steering by this moving lubber line the ship would zigzag 45 degrees each side of her mean course with a period of eight minutes. The winding key ships in the base and a starting and stopping knob is fitted. Verge glass has an inverted cap.
Card- A 6” Kelvin card is fitted instead of the usual 8” for this bowl. It is not known if these compasses were ever used at sea. White with black markings graduated to 1/4 points and quadrantally in degrees. Paper rim attached to centre ring, into which jewelled cap fits, by radiating threads.
Needle-Four pin needles suspended by threads from card. 2 x 2.75" (7cm) 2 x 2.25" (5.7cm)
Pivot-Brass spike mounted in brass tube attached to zig zag mechanism.
Bowl-This is a pattern 14 Thomson compass bowl in the base of which a clockwork mechanism has been fitted. This mechanism drives a second lubber line backwards and forwards across the true lubber. By steering by this moving lubber line the ship would zigzag 45 degrees each side of her mean course with a period of eight minutes. The winding key ships in the base and a starting and stopping knob is fitted. Verge glass has an inverted cap.
Card- A 6” Kelvin card is fitted instead of the usual 8” for this bowl. It is not known if these compasses were ever used at sea. White with black markings graduated to 1/4 points and quadrantally in degrees. Paper rim attached to centre ring, into which jewelled cap fits, by radiating threads.
Needle-Four pin needles suspended by threads from card. 2 x 2.75" (7cm) 2 x 2.25" (5.7cm)
Pivot-Brass spike mounted in brass tube attached to zig zag mechanism.
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Object Details
| ID: | ACO0049 |
|---|---|
| Type: | Dry card compass |
| Display location: | Not on display |
| Creator: | Thomson, William |
| Date made: | ca.1918 |
| Credit: | National Maritime Museum, Greenwich, London, Admiralty Compass Observatory |
| Measurements: | Overall: 165 mm x 275 mm x 280 mm |
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