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Fathom

A '''fathom''' is a Units of measurement|unit of length in the Imperial unit|Imperial system (and the derived United States customary units|U.S. customary units), used especially for measuring the depth of water. There are 2 yards (6 Foot (length)|feet) in a fathom.''Encyclopædia Britannica'' eleventh edition 1911. Based on the distance between the fingertips of a man's outstretched arms, its size varied slightly depending on whether it was defined as a thousandth of an Nautical mile|(Admiralty) nautical mile or as a multiple of the imperial yard. Formerly, the term was used for any of several units of length varying around 5 and 5½ feet. The name derives from the Old English language|Old English word ''fæðm'' meaning embracing arms or a pair of outstretched arms.''Oxford English Dictionary'', second edition, 1989;Fathom - Definition from the Merriam-Webster Online Dictionary. In Middle English language|Middle English it was ''fathme''. A ''brass'' was a unit of length equal to a fathom. A ''cable length'', based on the length of a ship's cable, has been variously reckoned as equal to 100 or 120 fathoms. At one time, a ''quarter'' meant a fourth of a fathom. Abbreviations: f, fath, fm, fth, fthm.

International fathom

One fathom is equal to:
- 1.8288 metres (1 metre is about 0.5468 fathoms)
- 2 yards (1 yard is exactly 0.5 fathoms)
- 6 Foot (length)|feet (1 foot is about 0.1667 fathoms)
- 18 Hand (unit)|hands
- 72 inches In 1959 the United States, Australia, Canada, New Zealand, South Africa, and the United Kingdom defined the length of the international yard to be exactly 0.9144 metre. With the adoption of the metric SI system the use of fathoms declined.

British fathom

The British Admiralty defined a fathom to be a thousandth of an Nautical mile|imperial nautical mile (which was 6080 ft) or 6.08 feet. In practice the fathom was always regarded as exactly 6 feet. No conflict in the real world existed as depths on Imperial nautical charts were indicated in feet if less than 30 feet and in fathoms for depths above that.

Use of the fathom

Water depth

Most nautical charts produced by hydrographic offices worldwide, with the notable except of those produced by the U.S. Hydrographic Office, which uses feet and fathoms, now indicate depths in metres. Nevertheless, most English-speaking mariners are familiar with the unit. A nautical chart will always explicitly indicate the units of depth used. To measure the depth of shallow waters, boatmen used a sounding line containing fathom points, some marked and others in between, called ''deeps'', unmarked but estimated by the user.Sounding lead. By James Mathews. Navy & Marine Living History Association. Water near the coast and not too deep to be fathomed by a hand sounding line was referred to as ''in soundings'' or ''on soundings''.Burney: "Vocbulary of Sea Terms", 1876. The area offshore beyond the 100 fathom line, too deep to be fathomed by a hand sounding line, was referred to as ''offsoundings'' or ''out of soundings''.MarineWaypoints.com - Nautical Glossary. SandyBay.net - Marine Directory (MarineWaypoints.com) and Reference Directory (StarDots.com). A ''deep-sea lead'', the heaviest of sounding leads, was used in water exceeding 100 fathoms in depth.The new way and the old; how the sounding machine has superseded the deep sea lead. The New York Times, June 6, 1892, page 5. This technique has been superseded by sonic depth finders for measuring mechanically the depth of water beneath a ship, one version of which is a is the '''Fathometer''' (trademark).''Field Procedures Manual'', National Oceanic and Atmospheric Administration (NOAA), Office of Coast Survey. May 2008. In chapter 7, Glossary, page 252. The record made by such a device is a '''fathogram'''.''Hydrographic Manual''. By Captain Karl B. Jeffers. Publication 20-2, Coast and Geodetic Survey, U. S. Department Of Commerce. Posted by the Hydrographic Society of America. A '''fathom line''' or '''fathom curve''', a usually sinuous line on a nautical chart, joins all points having the same depth of water, thereby indicating the contour of the ocean floor.Glossary of Marine Navigaion. Page 763. I'd Rather Be Sailing.

Line length

The components of a commercial fisherman’s setline were measured in fathoms. The rope called ''groundline'', used to form the main line of a setline, was usually provided in bundles of 300 fathoms. A single 50-fathom skein of this rope was referred to as a ''line''. Especially in Pacific coast fisheries the setline was composed of units called ''skates'', each consisting of several hundred fathoms of groundline, with gangions and hooks attached. A ''tuck seine'' or ''tuck net'' about 70 fathoms long and very deep in the middle was used to take fish from a larger seine. A ''line'' attached to a whaling harpoon was about 150 fathoms long. A ''forerunner'' — a piece of cloth tied on a ship's log line some fathoms from the outboard end — marked the limit of drift line. A ''kite'' was a drag, towed under water at any depth up to about 40 fathoms, that on striking bottom was upset and rose to the surface. A ''shot'', one of the forged lengths of chain joined by shackles to form an anchor cable, was usually 15 fathoms long.

Burial

It is customary, when burying the dead, to inter the corpse at a fathom's depth, or ''six feet under''. A burial at sea (where the body is weighted to force it to the bottom) requires a minimum of six fathoms of water. This is the origin of the phrase to ''deep six'', meaning to discard, or dispose of.

On land

Until early in the 20th century, it was the unit used to measure the depth of Mining|mines (mineral extraction) in the United Kingdom. Miners also use it as a unit of area equal to 6 square feet in the plane of a vein. In Britain, it can mean the quantity of wood in a pile of any length measuring 6 feet square in cross section.

Other fathoms and similar units of length

Units of length similar to the size of the fathom can be found in many cultures. Some are listed below.

Notes

References

External links

- An explanation of the fathom marks used at sea (retrieved Sept 2005).
- Fathom - LoveToKnow 1911. 1911 Encyclopedia Britannica - Free Online.
- Hungarian web page that refers to the length of a "bécsi öl" Category:Units of length Category:Human-based units of measure Category:Nautical terms

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