42:  How can I make Emacs automatically scroll horizontally?

  Use hscroll.el by Wayne Mesard <wmesard@esd.sgi.com>.  The current
  version of hscroll is 1.5 (November 1993), and should be included in a
  future Emacs distribution.  If you cannot find the package, write to
  Wayne directly.

  NOTE: The version at the Emacs Lisp Archive is out of date.  Check the
  version number before installing any copies of hscroll you might find!