For a teenage boy and an escaped slave to head south down the river in
1845 or so meant capture and re-enslavement for Jim and prison or worse
for Huck for aiding him. The only practical move for them is to paddle
north. Clemens had to figure out a way to keep that raft moving south to
Silas's farm, and the duke and the king's commandeering of it enabled him
to do  just that, while also enabling him to satirize royalty, religious
camp meetings, mob psychology, et cetera.

These are not totally original thoughts, but were brought out in
discussions at Bob Hirst's Twain course, the most fun I had at UC
Berkeley.

Gerald