[15] The 18th century was an epoch in which the world was opened up more and more and commerce with distant continents expanded greatly. Lengthy return voyages had to be undertaken, frequently lasting several years. The vesses were heavily-manned and built to be as sturdy and seaworthy as the best naval vessels. Their carrying capacity was limited and the vessels were not pressed particularly hard. Every vessel, every voyage was a great economic gamble. Carrying capacity and speed were matters of subsidiary concern, the most important thing being to return the vessel and its immensely valuable cargo in good condition.