Wine gallon
A wine gallon is a unit of capacity that was used routinely in England as far back as the 14th century, and by statute under Queen Anne since 1707. Britain abandoned the wine gallon in 1826 when it adopted imperial units for measurement. The 1707 wine gallon is the basis of the United States' gallon, as well as other measures.
The English and U.S. gallon are not the same volume, because of different basis for the pressure and temperature at which the volume is calculated. In England, the volume was measured at 63 °F and barometric pressure of 29.52, which was essentially room temperature. However, in the U.S., the volume was measured at 39.83 °F because Ferdinand R. Hassler, Superintendent of the Coast Survey (who was placed in charge of refining the definition of U.S. measurement standards), believed it to be the temperature at which water was at its maximum density (later discovered to be 39.2 °F). See also the report of Alexander D. Bache, Superindendent of Weights and Measures, 46-47. Ex. Doc. No. 73, 30th Cong., 1st sess.
Note also that the Imperial gallon was defined with yet another set of temperature and pressure values (62 °F and 30 in hg)
To convert a wine gallon to an Imperial gallon, multiply by 0.833111. To convert an Imperial gallon to a wine gallon, multiply by 1.200320.
Some research concludes that the wine gallon was originally meant to hold 8 troy pounds of wine. The 1707 British statute defines the wine gallon as 231 cubic inches (3,790 cm3) – e.g. a cylinder 7 inches (178 mm) in diameter and 6 inches (152 mm) high, c. 3.785 litre – and was used to measure the volume of wine and other commercial liquids such as cooking oils and honey. A 14th-century barrel of wine contained 31.5 gallons, which equals one-eighth of the tun of 252 gallons.
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