What is a unit of measure called a twain ?

Question

it was used by riverboats to check the depth of the river

Answer 1

Mark Twain was the pen name of Sam Clemens who at one time was a river boat pilot on the Mississippi River. Twain in that context meant 2(two). When the sounder man called out "By the mark twain" he had sounded the depth of water at that point as two fathoms, a fathom being six feet. The sounder was very important as the river bottom shifted often and the depth had to be taken constantly to keep from grounding a steamboat.

The sounder used a line with a weight on it to carry it to the bottom. It was marked at fathom intervals so that he could read the depth at a glance, so he would report" by the mark______"At twelve foot depth the water was mark twain.

Answer 2

it meant between,as in knots tied in a rope,to ensure adequate depth for the keel of the boat...

Answer 3

twain is Elizabethan English for two. a unit of measure used on steamboats using a lead weight and a line with knots tied at 3 foot intervals so  by the mark one or 3 feet between the bottom of the boat and the river bed and by the mark twain or 6 feet clearance. and so forth.

Answer 4

1. "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!"

Answer 5

Mark Twain (Samuel Clemens) took that name because of his working on/familiarity with the Mississippi River and the boats that worked the river.

When the boat workers needed to test the depth, they would put a measuring device (usually a marked rope) and call out the depth of the river. "Mark twain" meant "mark two" fathoms, or in other words, 12 feet.

http://hoover.archives.gov/exhibits/Miss...