After reading the book when he was 12, he read a dialogue between the mister and the mistress that changed him?

From the text:

I was now about twelve years old, and the thought of being ~a slave for life~ began to bear heavily upon my heart. Just about this time, I got hold of a book entitled "The Columbian Orator." Every opportunity I got, I used to read this book. Among much of other interesting matter, I found in it a dialogue between a master and his slave. The slave was represented as having run away from his master three times. The dialogue represented the conversation which took place between them, when the slave was retaken the third time. In this dialogue, the whole argument in behalf of slavery was brought forward by the master, all of which was disposed of by the slave. The slave was made to say some very smart as well as impressive things in reply to his master-- things which had the desired though unexpected effect; for the conversation resulted in the voluntary emancipation of the slave on the part of the master.