mark twain, not the man, the measurement?

Question

what are the other marks one using this parlance would use. the whole vocabulary and corresponding meanings would be great.

Answer 1

According to:
http://www.dvdjournal.com/quickreviews/m/marktwain.q.shtml

"When the great steamboats traveled the Mississippi River in the 19th century, it was customary to measure the water's depth with a rope marked with knots — a particularly important chore in a river such as the Mississippi, with its many curves, currents, and shallows. The minimum safe depth for a steamer normally was 12 feet, also known as two fathoms or the simple boatman's cry "mark twain!"

The article found at this site is pretty interesting. Several paragraphs are devoted to riverboat jargon, from the meaning of "stage" and "possum" to "buryin' a dead man".
http://www.louisianafolklife.org/LT/Articles_Essays/creole_art_big_river_trad.html