Mysteries of Measurements

Have you ever wondered why 12 inches are called a "foot"? Or who decided how long an inch would be, or how many feet should make up a mile? And if a horse race is two furlongs, how long is that?

The system of measurement that we use today in the United States is full of such mysteries. Most of the basic units of measure have been around since ancient times, when people used various parts of the body as standards because they were readily available and easy to use. However, that leaves a lot of room for variation and uncertainty in measurements.

The cubit, for example, is a unit of measure that was widely used in the ancient world; it equaled the distance from the elbow to the longest fingertip. Its length varied from 17 to 25 inches, undoubtedly because people’s arms are different lengths. One of the earliest records of the use of a cubit is in the building of Noah’s ark. According to the Bible, the ark was 300 cubits long, 30 cubits high, and 50 cubits wide. Since there was no standard for the length of the cubit, that means that the ark would have been about 141 to 208 yards long, by 14 to 21 yards high, by 24 to 35 yards wide.

The yard was one of the first measures to have an official standard. In 1120 King Henry I of England defined the official yard as the length from the tip of his nose to the end of his thumb. As a child I watched my mom, who worked in a fabric store, take a quick measure of a yard of cloth from her nose to the end of her outstretched arm. Later the measurement was checked against a yardstick, and was always pretty close.

In 1150, 30 years later, King David I of Scotland set a legal standard for the inch. Since the technology didn’t exist to make a model of exactly one inch and send it to everyone in his kingdom, he decreed that the official way to determine an inch would be to select a small man, a medium-size man and a large man, measure the bases of their right thumbnails, and take an average of the three measurements. It seems fairly cumbersome, but at least that way the inch in one village would closely approximate the inch in the next village.

The foot has been used as a measure from earliest times, but its length has varied from 11 to 14 inches. Since few people have feet that are 14 inches long, that measure might have been made of a foot in a heavy boot. The Romans divided their official foot into twelve parts, each an uncia, or thumb width. Uncia means “one-twelfth” or “inch.”

The “rod” was a legal standard used in surveying land. Having a uniform standard for the rod was crucial in determining property rights. The legal standard was once determined this way: an official, such as the mayor, would stand outside a church on a Sunday morning and pick the first sixteen men who came out. Lining up their left feet one behind the other, he would measure their total length. This procedure gave a reasonably standard measure which could be duplicated anywhere.

In order to measure longer distances, the Romans counted the number of paces as they marched from one town to the next. A military pace is the walking distance from putting down one foot until it is lifted and put down again, about 5 feet. Since the Latin word for one thousand is mille, a distance of one thousand paces was called mille passus, which later became mile. The Roman mile of 5000 feet was the standard for hundreds of years.

The furlong was originally the length of one furrow (furrow-long) in a plowed field – equal to 40 rods or 220 yards. This made the length of eight fields (8 furlongs) 280 feet longer than the official mile of 5000 feet. Since measuring land was easier if the furlong divided equally into the mile, the “country mile,” an unofficial unit of measure, came into common use. It was 280 feet longer than the official mile.

Apparently having two different measures for the mile became frustrating for both landowners and mapmakers. In the 1500s, Queen Elizabeth I of England declared that the mile should officially be equal to 8 furlongs, giving us the modern length of 5280 feet.

Over the centuries people have used great inventiveness in finding ways to measure things. So next time you use your ruler, jog a mile or buy a yard of fabric, remember all the elbows and thumbnails, kings and queens, marching soldiers and plowed fields behind the mysteries of our measurements.