He added copper rivets at the corners of the pockets to keep the stitches from tearing.
Historically the particular routes were also shaped by the powerful influence of winds and currents during the age of sail. For example, from the main trading nations of Western Europe, it was much easier to sail westwards after first going south of 30 N latitude and reaching the so-called "trade winds"; thus arriving in the Caribbean rather than going straight west to the North American mainland. Returning from North America, it is easiest to follow the Gulf Stream in a northeasterly direction using the westerlies. A triangle similar to this, called the volta do mar was already being used by the Portuguese, before Christopher Columbus' voyage, to sail to the Canary Islands and the Azores. Columbus simply expanded this triangle outwards, and his route became the main way for Europeans to reach, and return from, the Americas.
Atlantic triangular slave trade
See also: Atlantic slave trade and Slave Coast of West Africa
The best-known triangular trading system is the transatlantic slave trade that operated from Bristol, London, and Liverpool. during the late 16th to early 19th centuries, carrying slaves, cash crops, and manufactured goods between West Africa, Caribbean or American colonies and the European colonial powers, with the northern colonies of British North America, especially New England, sometimes taking over the role of Europe. The use of African slaves was fundamental to growing colonial cash crops, which were exported to Europe. European goods, in turn, were used to purchase African slaves, who were then brought on the sea lane west from Africa to the Americas, the so-called Middle Passage. Despite being driven primarily by economic needs, Europeans sometimes had a religious justification for their actions. In 1452, for instance, Pope Nicholas V, in the Dum Diversas, granted to the kings of Spain and Portugal "full and free permission to invade, search out, capture, and subjugate the Saracens [Muslims] and pagans and any other unbelievers ... and to reduce their persons into perpetual slavery."
