Fathom

A fathom is a unit of length in the Imperial system (and the derived U.S. customary units). The name derives from the Old English word fæðm meaning 'a pair of outstretched arms'.^[1][2][3] In Middle English it was fathme. Its size varied slightly depending on its base definition, either based on a thousandth of an (Admiralty) nautical mile or as a multiple of the imperial yard. There are 2 yards (6 feet) in a fathom.^[4]

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)
• 4 cubits (1 cubit is exactly 0.25 fathoms)
• 6 feet (1 foot is about 0.1667 fathoms)
• 18 hands
• 72 inches

In 1954 the United States and countries of the Commonwealth of Nations defined the length of the international yard to be exactly 0.9144 metres. 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 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

The fathom is now of mainly historical interest: it is now an obsolete unit and has not been used in maritime affairs for decades. All nautical charts produced by Hydrographic Offices worldwide (except for those produced by the U.S. Hydrographic Office, which uses feet) indicate depths in metres. Until early in the twentieth century, it was the unit used to measure the depth of mines (mineral extraction) in the United Kingdom.^[5]

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.^[6]

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.

See also

• English unit
• Imperial unit
• United States customary units
• International System of Units
• Ancient Greek units of measurement

Notes

References

• Fenna, Donald (2002). A Dictionary of Weights, Measures, and Units. Oxford University Press. ISBN 0198605226. 

External links

• An explanation of the fathom marks used at sea (retrieved Sept 2005).
• Hungarian web page that refers to the length of a "bécsi öl"da:Favn

de:Klafter et:Süld es:Braza (unidad) eo:Klafto fr:Brasse (unité de mesure) he:פאתום hu:Öl it:Braccio (unità di misura) nl:Vadem ja:ファゾム no:Favn pl:Sążeń ru:Морская сажень sl:Seženj fi:Syli sv:Famn