Elementary arithmetic, with brief notices of its history... by Robert Potts.

10;
In these conclusions, the lineal unit, as also the square unit and the
cubic unit, though limited in magnitude, are not restricted to any
standard unit, but may be any multiple or submultiple of any standard
unit whatever. These units may be increasel or diminished in any
degree, and consequently, the products which express the square
units in any area, and the cubic units in any volume, may be denoted
either by fractional or decimal numbers.
The Act for Imperial Weights and MIeasures, passed on 17th June,
1824, has declared that a certain brass rod is the standard yard of
England. That its length, compared with that of the seconds pendulum at the level of the sea, is in the proportion of 36 to 39-1393 inches,
the latter being the exact length of the seconds pendulum in a vacuum
in the latitude of London.
MEASURES OF LENGT1I.
3 barleycorns are equal to 1 inch
12 inches,, 1 foot
3 feet,, 1 yard
5~ yards,, 1 rod, pole, or perch
40 poles,, 1 furlong
3 furlongs,, mile
691 or 60 geographical miles 1 degree.
There are other measures employed in different trades and employments, as the palm of 3 inches, and the hand of 4 inches, the
cubit of a foot and a half, the fathom of 6 feet, and the larger unit of
a league of 3 miles.
Engineers divide the inches into tenths as a more convenient
division for small portions than eighths or twelfths.
The chain devised by IMr. Gunter, and called after his name, is
22 yards long, and consists of 100 links, so that 80 chains are equal
to one mile. The practical use of this chain, both for measuring
lengths and surfaces, led to its adoption, and it has continued in use
both for the measuring of distances and surfaces, 10 square chains being
equal to one acre.
MEASURES Or SURFACE.
144 square inches are equal to 1 square foot
9 square feet,, 1 square yard
304 square yards,, 1 square rod, pole, or perch
40 poles,, 1 rood
4 roods,, 1 acre
640 acres,, 1 square mile.
Paper is measured by considering 24 sheets to one quire, and 20
quires to a ream. The ream of 20 quires is called the mill ream, and
is different from the printer's ream, which consists of one quire and a
half more than the mill ream. These numbers do not describe the
size of the sheets of paper, which are of various sizes and different
names.