The name is derived from the Latin word for elbow ( cubitum). cubit A cubit is the distance from the elbow to the tip of the middle finger on a man's arm. A standard foot is 12 inches or 304.8 mm exactly. foot A foot is the length of a man's foot - a convenient measuring tool for men with feet. It was traditionally used to measure the height of horses and not much else as far as I can tell. hand A hand is the width of a man's hand measured across the palm and including the thumb. One inch is now defined as exactly 25.4 mm. The inch is commonly subdivided into halves, quarters, eighths, sixteenths, and other powers of two but can also be divided into hundredths (as in the caliber of firearms) or thousandths (called thou in the UK and mils in the US). The Romans brought the concept of the 12 inch foot to England when they invaded in the year 43 and left it behind when they were expelled in the year 409. The word inch comes from the Latin word for one-twelfth ( uncia). inch An inch was originally the width of a man's thumb, but was later defined as the length of three barleycorns placed end to end. There are a lot of "nice" numbers in this system - numbers like 3, 4, 5, 6, 8, 12 and 16 - but after a while the "nice" numbers put you through combinatoric gyrations that bring computational pain and suffering. Feet don't fit into furlongs in an easy to grasp way. Unfortunately, the conversion factors are a mess. Furlongs, fathoms, miles, yards - these make sense if you know a little bit of etymology (the study of the origin and evolution of words). Hands, feet, rods, paces - these are things most of us can relate to. The English system is composed of a lot of sensible length units. The rest of the discussion follows this sequence: traditional units (length, mass, area, volume), non-metric scientific units (the foot-pound-second system s), and then let's try to end it. Let's just say they evolved in ways that were more organic and less logical than the SI units. This intro should talk about the cultural origin of these traditional units, but I haven't decided what to write yet. Their method became absolutely necessary when people came to deal in many commodities, and in great quantities of them. But by a little observation, they found that one man's arm was longer or shorter than another's, and that one was not to be compared with the other, and therefore wise men who attended to these things would endeavour to fix upon some more accurate measure, that equal quantities might be of equal values.
In like manner there were natural measures of quantity, such as fathoms, cubits, inches, taken from the proportion of the human body, were once in use with every nation.
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