Tuns, Tons and Barrels of Wine by Thomas Hale
The landsman must often think that seamen try to make their "Why I pay tax on whole ship? I no pay tax on deck house or calling sound complex by using archaic and unusual terms, galley. I pay tax on cargo holds on ly!" And thus was born the thu s giving the impression that their profess ion is beyond the distinction between gross tonnage and net tonnage. Most deck comprehension of ordinary mortals .. Certainly, the maritime houses and cabins above the main deck are not even included community has managed to obscure and confuse the simple in gross tonnage. To get the net tonnage, other areas, such as word ton such that even admiralty lawyers have stumbled over engine room, fue l tanks, store rooms, chain lockers and crews' the proper definition or usage of the word . Sorting out the quarters are subtracted from the gross tonnage. meanings and the history of thi s word has been an intriguing Register tonnage is also an important term and is the search. tonnage appearing on the vessel 's register, i.e. the document "A pint 's a pound the world around," or is it? The old saying under which she is registered at her home port and under which may be accurate up to a point, for, indeed, one pint of water she sails. It will be stated as gross tonnage and/or net tonnage weighs about a pound , or 1.04 lbs to be exact. A pint of and refers to the volumetric capacity of the ship in units of 100 bourbon , however, weighs onl y .82 lbs, whereas a pint of cubic feet. Documented yachts or small commerc ial vessels sulfuric ac id weighs almost two (1.89). But have their documented tonnage carved or suppose we are talking about green beans. otherwise permanently affixed to the strucNow we have 16 pints in something called a ture of the boat, reading, for example "Net peck, and who knows what a peck of beans 18." This always refers to the net interior weighs? Similarl y, in a maritime context, the cubage of the craft in tons, not, as is often use of the word ton sometimes refers to w:eight mistakenly ass umed, to her weight in tons. and sometimes refers to volume. Often the The operator of a boatyard marine railway or same word can have totally different meantravel-lift will do well to understand this fact! ings . When I was a little boy, I well remember Since the beginning, a ton was the index the coal truck backing into our driveway and upon which taxes or other charges were levied the roar as two tons of coal disappeared down on a vessel. Taxes or customs duties on ships the shiny chute into the; cellar coal bin to be and cargoes are among the earliest of the attacked by a burly Irishman with a shovel world 's records, and there are records of taxes who stoked the family furnace. A ton of coal on the import of cedar from Lebanon into weighed 2,000 lbs, a simple enough concept, ancient Egypt and innumerable Greek and and for years I thought it was always so. Roman records of taxes on amphorae of olive A ton of coal may indeed weigh 2,000 lbs oil or wine, or of hides or wool. It was a tax on ~ to most of us . But when the mariner refers to a cargo of tea that sparked the unpleasantness "' a ton (weight) he is talking about a British between King George III and the Thirteen ~ "long ton" which equals 2,240 lbs or 35 cubic Colonies. Thus, there have long been tax ~ feet of salt water, unless he is a Frenchman, collectors in every port, but how and what to ts who will only speak of "tonnes" (metric tax? How to measure the cargo? ~ tons) which equal 2,204.6 lbs, just to confuse the issue. But for now, let's just accept During the Middle Ages and the earl y ~ Renaissance, the most common cargoes, es- : ; : the long ton as a unit of weight. "But," you pecially in the Mediterranean, where most of ~~---------~ may say, "you just defined tonnage as a unit the seaborne trade was conducted, were casks of volume. Why not leave it there?" Simply of wine commonly called tuns. They were relatively tall and because there are many situations in which it is weight rather narrower than what we think of today as casks or hogsheads, than volume that is important. Obviously a ship might be able but they became quite standardized, so that a tun of wine in to carry I00 tons (volume) of bourbon whiskey, weighing Spain was roughl y the same as a tun of wine in Sicily or Malta about 5 I lbs per cubic foot , but would be able to carry safely or in Tyre or Sidon. So, it was natural for customs men and tax onl y a fraction of this cubage were she transporting lead, coll ectors to base their charges on a ship in terms of the tuns which weighs 750 lbs per cubic foot. In order to define a it carried. Cubic capacity, not weight, was the criterion. vessel's weight or weight-carrying capacity, a wholly differUnfortunately, over the years the spelling became corrupted to ent set of terms emerges- unfortunately still defined in terms ton , leading to the inevitabl e confusion between weight and of tons- long tons this time. volume. At some point the volumetric measure became stanA ship's displacement tonnage is just that, i.e. the weight of dardized at 252 gallons of wine to the ton, but fin ally the water in long tons which the vessel displaces. It is arrived at by accepted volume was defined as 100 cubic feet per ton (tun) calcul ating the volume of water displaced in cubic feet and and vessels were and are still often taxed and described by their dividing by 35 (35 cubic feet of sea water equall ing I long ton). cubic tonnage. Thus, a thousand ton ship would have an Thus, in effect, displacement can be considered a volumetric enclosed capacity of 1,000 times I 00, or l 00,000 cubic fee t. measurement expressed in weight. It took me a long time to So far, except for the confu sion over the two definiti ons of reconcile this concept! There are actually two measurements the same word, the language is not too compl icated. But, now of displacement: first, displacement light, which measures the the bureaucrats and technicians and lawyers enter the picture, ship 's weight minus her food, stores, fuel and cargo; second, and in their efforts to further define the word, they have displacement loaded, which includes all her consumable stores muddied the waters. and cargo. At one time in the dim distant past, some angry sea lawyer Dead weight tonnage is the difference between displaceshook his fi st under a customs collector's nose and shouted, ment tonnage loaded and displacement tonnage light. It accu-
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SEA HISTORY 58 , SUMMER 199 1