Answer:
The author uses verbal irony in that they describe the sellers of slaves as 'sinning expertly and genteelly, so as not to shock the eyes and sense of respectable society'. The author describes a horrific act as being performed efficiently and neatly. They tell of how you would be 'courteously entreated to call and examine, and...find an abundance of husbands, wives, brothers, sisters, fathers, mothers, and young children, to be "sold separately, or in lots to suit the convenience of the purchaser.' They also provide verbal irony in stating that "{the} soul immortal, once bought with blood and anguish by the Son of God, when the earth shook, and the rocks rent, and the graves were opened, can be sold, leased, mortgaged, exchanged for groceries or dry goods, to suit the phases of trade, or the fancy of the purchaser", They proceed with a complex and heavy description of the saving of human souls, and contrast it with the simple measures necessary to purchase slaves.