Bill McNeil, age 13, of Salt Lake City, Utah, for his question:

How did the nautical knot originate?

The speed of a ship is measured in knots, which are units of miles per hour. To a sailor, the fellow who says that a ship is making 20 "knots per hour" is a land lubber. The land mile of 5,280 feet grew from a bodge podge of linear measuring units. The nauti¬cal mile of 6076.1033 feet is a precise segment of the earth's circumference, which is a spinning circle measured in units called degrees, minutes and seconds. The mariners of old sailing ships had compasses, but they needed a device to measure speed and distance traveled. This device was the log chip and line.

The log chip was a quarter disk, weighted around the curve to make it point upward in the water. Strings attached it to a sturdy line and the line was knotted at precise inter¬vals of 47 feet, 3 inches. The chip was dropped in the wake of the ship and the line un¬rolled from the ship. After 28 seconds, the number of knots in the unrolled line were counted. This number was used to figure the speed of the ship was making 10 knots    or 10 nautical miles per hour.