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This early 20th Century model was made by Negretti & Zambra, London and was retailed to appeal to surveyors mainly for use in mining operations. Other features found on modern orienteering compasses are map and romer scales for measuring distances and plotting positions on maps, luminous markings on the face or bezels, various sighting mechanisms (mirror, prism, etc.) for taking bearings of distant objects with greater precision, gimbal-mounted, "global" needles for use in differing hemispheres, special rare-earth magnets to stabilize compass needles, adjustable declination for obtaining instant true bearings without resorting to arithmetic, and devices such as inclinometers for measuring gradients. [18] The sport of orienteering has also resulted in the development of models with extremely fast-settling and stable needles utilizing rare-earth magnets for optimal use with a topographic map, a land navigation technique known as terrain association. [19] Many marine compasses designed for use on boats with constantly shifting angles use dampening fluids such as isopar M or isopar L to limit the rapid fluctuation and direction of the needle. [20]
Admiralty, Great Britain (1915) Admiralty manual of navigation, 1914, Chapter XXV: "The Magnetic Compass (continued): the analysis and correction of the deviation", London: HMSO, 525 p. Needham, Joseph (1986) Science and civilisation in China, Vol. 4: "Physics and physical technology", Pt. 1: "Physics", Taipei. p. 252 Caves Books, originally publ. by Cambridge University Press (1962), ISBN 0-521-05802-3 All lensatic military compasses are the same when it comes to parts and features, so your choices will be a bit limited. Your deciding factors when purchasing one are likely to be its quality, finish or appearance, and budget. Main article: Magnetic deviation A binnacle containing a ship's standard compass, with the two iron balls which correct the effects of ferromagnetic materials. This unit is on display in a museum. FLUORESCENT】: The interface of the compass glows in the dark( please put it under light or sunshine 1~3 mins), so you can still use it even when night falls.L & M trace their roots to two London based Jewish families, who set up operations all over the world, initially in London and then the Indian subcontinent. Kreutz, Barbara M. (1973). "Mediterranean Contributions to the Medieval Mariner's Compass". Technology and Culture. 14 (3): 367–383. doi: 10.2307/3102323. JSTOR 3102323. S2CID 111540460.
You also get a variety of extra features such as a tripod screw hole on the base, built-in bubble level, folding thumb ring, ruler units on the side calibrated in inches and centimeters, thermo-elastic liquid-filled capsule holding a floating capsule, as well as a rotating bezel ring.In good condition, the body is engraved 'PATENT NO 1926. MADE BY F. BARKER & SON LONDON FOR CASTANON MONGEY. CIA MADRID. 4751'. A substantial compass weighing just under 800 grams and measuring 5 ½ (135mm) square, it's visually very impressive, despite the fact that it's had noticeable repair work on the lid and hinge ( see photos). Another thing to note, the compass has been calibrated in inches and millimetres to make for easy reading. In good original condition, the case is free of any dents and the card dial has only minor scuffing around the makers name.
Ministry of Defence, Manual of Map Reading and Land Navigation, HMSO Army Code 70947 (1988), ISBN 0-11-772611-7, 978-0-11-772611-6, ch. 8, sec. 26, pp. 6–7; ch. 12, sec. 39, p. 4 Declination here refers to the angle that measures the difference in degree between these two points.The double broad arrow also shows it was later officially decommissioned for sale into the civilian market. Dennison compasses from the World War I period have always been highly sought after by collectors, but this example is particularly special as it comes with its original Dennison branded box. This means you’ll either have to carry a portable charger or bring along a few extra batteries. On the other hand, analog compasses don’t require an external source of power.
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