Public domain image more than 100 years since creation, therefore further sourcing not required. 
Arab Slave Traders. A 19th-century engraving depicting an Arab slave-trading caravan transporting black African slaves across the Sahara. The trans-Saharan slave trade developed in the 7th and 8th centuries as Muslim Arabs conquered most of North Africa. The trade grew significantly from the 10th to the 15th century and peaked in the mid-19th century
19th-century engraving, probably from illustration by John Frederick Lewis (d. 1876)
19th-century
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