I've received a question by e-mail from someone who doubts that "grashoppering" did really work to get a steamboat over a sandbar and wasn't just used to get it back off the sandbar moving backward ... Guess there is no question that it did work, but does anyone know abut a source where it's being described very much in detail how that worked, to literally step-by-step lifting a steamboat over a sandbar?

Thanks!
Franz