Whether this prophecy is ever fulfilled or not, it is nevertheless plain that a very different-looking class of people are springing up at the south, and are now held in slavery, from those originally brought to this country from africa; and if their increase do no other good, it will do away the force of the argument, that god cursed ham, and therefore american slavery is right. if the lineal descendants of ham are alone to be scripturally enslaved, it is certain that slavery at the south must soon become unscriptural; for thousands are ushered into the world, annually, who, like myself, owe their existence to white fathers, and those fathers most frequently their own masters.

question 2
what is the allusion in this passage and its interpretation?

"thousands are ushered into the world"; although some slaves have white fathers, they are still lineal descendants of ham and should remain slaves.
"thousands are ushered into the world"; since some slaves have fathers, they should not be enslaved.
"the descendants of ham"; since some slaves have white fathers who are not the sons of ham, they should not be enslaved.
"the descendants of ham"; although some slaves have white fathers, they are still lineal descendants of ham and should remain slaves.