Tun (unit)
The tun is an English unit of liquid volume, used for measuring wine, oil or honey. Typically a large vat or vessel, most often holding 252 wine gallons, but occasionally other sizes were also used. The modern tun is about 954 litres.
The word tun is etymologically related to the word ton for the unit of mass, the mass of a tun of wine being approximately one long ton, which is. The spellings "tun" and "ton" were sometimes used interchangeably.
History
Originally, the tun was defined as 256 wine gallons; this is the basis for the name of the quarter of 64 corn gallons. At some time before the 15th century, it was reduced to 252 wine gallons, so as to be evenly divisible by other small integers, including seven.In one Early Modern English example from 1507, a tun is defined as 240 gallons.
With the adoption of the Queen Anne wine gallon of 231 cubic inches in 1706, the tun approximated the volume of a cylinder with both diameter and height of 42 inches. These were adopted as the standard U.S. liquid gallon and tun.
When the imperial system was introduced in 1824, the tun was redefined in the UK and its colonies as 210 imperial gallons. The imperial tun remained evenly divisible by small integers. There was also little change in the actual value of the tun.
Standard tuns of wine came to serve as a measure of a ship's capacity.
Definitions
In the US customary system, the tun is defined as 252 US fluid gallons, or exactly.In the imperial system, the tun is defined as 210 imperial gallons, or exactly.