"Tonnage"

The measure of a ship's cargo capacity is thought to have originated in the 13th century.

At that time, one of the most widely carried cargoes was wine in large casks known as

"tuns" An english tun contained approximately 250 gallons

of wine and weighed some 2,240 pounds.

When european nations started colonizing the Americas,

"tun" had become "ton".

The weght remained unchanged, but the volume assigned

per ton had increased from 57 cubic feet under

the old measure to 100 cubic feet by the 17th century.

Tonnage of ships using English ports was estimated using a simple formula

Length of keel X width

of hull X depth of hold

----------------------------------------- = burden

constant

The constant was changed from time to time, the

constant was 100 for much of the 1600s

but was changed to 94 in 1694, when a ton was refigured

at 94 cubic feet. Ships of 200 to 400 tons were

commonplace in the 17th century, although

some huge ships of 1000 tons or more existed