I came across this note in Fear's Day By Day:

Note: Arthur L. Scott’s article, “The Innocents Adrift Edited by Mark 
Twain’s Official Biographer,” PMLA, Vol. 78, No.3, (June, 1963), p.230-7 
covers in depth how Paine butchered this piece, which was initially to 
be a full-length book. Paine changed the title to “Down the Rhone” and 
the castrated version was published in Europe and Elsewhere, 1923.

and read through the article.  Now I'm wondering if transcripts of 
Twain's original manuscripts are available.