This painting—by S. Hutchinson—depicts slave-trading in action. Currently maintained by the National Maritime Museum (in London, England), this watercolor - c. 1793 - is entitled "Slave Traffic."
After the collapse of the Roman Empire, systematic slavery was virtually non-existent until it was reintroduced as a source of labor for the “New World.” The story of how African men, women and children were first captured, then shipped out as slaves for the colonial world, is appalling. Thanks to the Library of Congress, we can view surviving drawings and pictures of those disturbing times.
What they endured aboard ship, as they sailed to the Americas, was no less horrific:
Arriving in an unfamiliar country, where people did not speak their language, captured Africans were bought and sold at auction. Such was expected in the world of chattel slavery.