Shipping was the lifeblood of the Atlantic economy in the eighteenth century; shipping patterns were the arteries through which the merchants and commodities of the North Atlantic trading world were drawn together into an international commercial network. Ships making transatlantic voyages from British ports picked up the northeast trade winds around the latitude of Madeira and sailed three thousand miles to their destinations. This was the first leg of a passage that involved unloading and reloading cargoes, time spent in colonial waters, a complex shipping schedule, and possibly multilateral trading connections before vessels caught the prevailing southwesterlies near Newfoundland back to Europe. This long haul on ‘the busiest ocean highway in the world in the mid-eighteenth century’, was dominated by problems of time and space – time, because ships usually took the best part of a year to make a round-trip; space, because markets around the North Atlantic were decentralised and fragmented. Atlantic crossings were also partly constrained by the Navigation Acts, which not only confined trade within the empire to British and colonial ships and seamen but ‘enumerated’ certain commodities produced in British colonies that could not be shipped directly to foreign countries. Among these products were sugar, tobacco, indigo, furs, and naval stores. Because the Navigation Acts allowed free and equal competition for shipping services between individual parts of the empire, merchants had many possible options with regard to shipping patterns.

Despite their importance, the Atlantic shipping routes of the eighteenth century have never received the attention they deserve.