[LAU] thunderstorm

[TheOther]

Fons Adriaensen wrote:
> On Tue, Jun 23, 2009 at 08:11:30AM -0500, TheOther wrote:
> 
>> Let's see, there's 640 acres to a section, and a section of
>> land is 1 mile by 1 mile, or a 1 mile square. 
> 
> Incredible, those units !
> 
> So a square piece of one acre would have a size of
> 1 mile / sqrt(640). That square root is not an integer.
> 
> Is this the definition of 1 acre ?
> 

Hello Fons,

You can Google an acre for the definition.  I found this definition to 
be accurate and somewhat easier to understand:

The Question:

We are trying to find feet measurement for an acre—not the square 
footage. Can you please help?
The Answer:

Because an acre is a measure of area, not length, it is defined in 
square feet. An acre can be of any shape—a rectangle, a triangle, a 
circle, or even a star—so long as its area is exactly 43,560 square feet.

The most standard shape for an acre is one furlong by one chain, or 
660 feet by 66 feet. To find the linear measurements of other 
rectangular acres, just divide 43,560 by the number of feet you want 
on one side. A square-shaped acre would then be about 208.7 by 208.7 
feet (because 208.7 x 208.7 = ~43,560). An acre 100 feet wide would be 
435.6 feet long (100 x 435.6 = 43,560) and an acre 1 foot wide would 
be 43,560 feet long.

The acre, by the way, was originally an English unit of measurement 
that described the area that a yoke of oxen could plow in a day. It 
originally differed in size from one area to the next, but was 
ultimately fixed at 4,840 square yards, or 160 square chains (its 
current size).

—The Editors

Note, you also get the definition of a furlong (sometimes still used 
in American horse racing for the length of the race).  A furlong is 10 
chains.

Then for the definition of a chain:

A chain is a unit of length; it measures 66 feet or 22 yards or 4 rods 
or 100 links. There are 10 chains in a furlong, and 80 furlongs in one 
statute mile. An acre is the area of 10 square chains (that is, an 
area of one chain by one furlong). The chain has been used for several 
centuries in Britain and in some other countries influenced by British 
practice.


Some legal descriptions of plots of land in the USA still use these 
antiquated measurements.  Back in my surveying days, this nearly 
always required having good math skills or a calculator handy for the 
conversions!

Best,
Stephen.