how did europeans profited at the expense of African Americans during the era of the Atlantic slave trade?

Answer 1

Here is a good article about that:

http://africanhistory.about.com/library/weekly/aa080601a.htm

European countries owned most of the American colonies that benefited from the trade, by facilitating agriculture in warm climates. European countries (espcially Portugal) also owned the African colonies from which most of the slaves were exported, and benefited ecnomically from their sale.

Answer 2

what is the former slave that traveled the contry to speak out against slavery