So Cass put his free Negroes on a boat bound upriver, and never heard of them again. (4.150)
Some of these former slaves may have reached freedom and managed to have a decent life, in spite of what Cass thinks. He thinks he sent them away because he "cannot bear their eyes upon him." In his case the people he freed look at him as a hero. His shame is in not being able to live up to his potential as a advocate of equal rights.
In any case, he laid aside the journal and entered upon a period of the Great Sleep. (4.166)
The piece of American history that Jack encounters in the Cass Mastern story is so shocking to Jack that he temporarily disassociates from the world. He can no longer understand where he is in space, time, or history.