Historically why is a rod 16.5 feet?

Answer 1

A rod is factored by links, not by inches. A link is equal to 7.92 inches; therefore, a rod is 25 links.

Rods - a little more commonly called poles, or sometimes called perches - is part of a system of area measures that was parallel to our customary system of linear measure (inches, feet, yards, miles).

1 link = 7.92 inches

25 links = 1 pole or rod or perch

100 links = 1 chain = 4 poles = 66 feet

250 links = 1 fartherling = 10 poles = 165 feet

10 chains = 1 furlong = 40 rods = 8 fartherlings = 660 feet

8 furlongs = 1 mile

For AREA, an acre is 1 furlong in length and 1 chain in width, i.e. 660 feet x 66 feet. Or, 1 fartherling by 4 chains. Or, 165 feet by 264 feet.

English gardeners will know that a gardening "allotment" is 10 poles by 1 pole, AKA 1 fartherling by 1 pole or rod, or 165 feet by 16.5 feet (which is 5.5 yards). A cricket pitch is 1 chain long - 66 feet (22 yards).

The "why" for all of this is that land, like time, is precious, and this is a super-divisible system.

Another way of looking at this is that it's a system whose basic factors are 10, 11, and 12, in different combinations. So, for example, an acre of land with its 43,560 square feet can be divided quite easily in any number of combinations without ever deviating from good whole numbers (it's directly divisible, for example, by every number between 1 and 12 except 7).

It was a neat and quite sophisticated system; and if you think about it, had a lot more mathematical capability than the inflexible metric system.