Knot

Knot, the divisions of the log-line on board ship (marked by knots), each having the same relation to a geographical mile as twenty-eight seconds has to an hour. Hence the number of knots in the log-line which run out in twenty-eight seconds represents the number of geographical or nautical miles an hour which the ship is going at the time. The geographical mile is $\backslash frac\{1\}\{60\}$th of a mean degree of a meridian on the earth (see DEGREE), and is therefore $\backslash frac\{1\}\{60\}$th of 69.055 English statute miles; hence when a ship is going '13 knots,' it is travelling really at the rate of about 15 English miles an hour. See LOG.