has been estimated that it cost less for a sailing ship of the Roman Empire to carry grain the length of the Mediterranean than to move the same amount 15 miles by road. Rome consumed about 150,000 tons of Egyptian grain each year over the first three centuries AD.

A similar but more recent trade in coal was from mines situated close to the River Tyne to London - which was already being carried out in the 14th century and grew as the city increased in size. In 1795, 4,395