A measurement is a comparison. We measure the length of a lot by
comparing it with the standard of length, the yard or foot. We measure
a farm by comparing its area with the standard unit of surface measure,
the acre, square rod, or square yard.
In every measurement we must first have an accepted standard unit.
The history of units of measurement is a very interesting one, and
its difficulty arises from the fact that no two things in nature are
the same. One of the ancient units of length was the cubit, supposed
to be the length of a man's forearm, from the elbow to the end of the
middle finger. This, like other natural units, varied and was therefore
unreliable. As civilization progressed it became necessary for the
various governments to take up the question of units of measurements
and to define just what they should be.
Our own standards are copied from those of Great Britain, and although
congress is empowered to prescribe what shall be our units, little has
been changed, so that with few exceptions we are still using English
measurements.
The almost hopeless confusion and unnecessary complication of figures
is shown in the following tables as compared with the metric system:
12 inches = 1 foot .001 = millimetre
3 feet = 1 yard
(standard) .01 = centimetre
5-1/2 yards } .1 = decimetre
or } = 1 rod
16-1/2 feet } 1. = metre
320 rods } 10. = dekametre
or }
1760 yards } = 1 mile 100. = hectometre
or }
5280 feet } 1000. = kilometre
The original English definition of an inch was "three barley corns"
with rounded ends. The meter is 1/10,000,000 (one ten-millionth)
of a quadrant of the earth's circumference, _i. e._, the distance
from the pole to the equator measured along one of the meridians
of longitude. The length of three barley corns might be different
from the next three, so here was the original difficulty again. The
designers of the metric system went back to the earth itself as the
only unchangeable thing--and--are we sure there is no change in the
earth's circumference? The great advantage of the metric is that it is
a decimal system and includes weights as well as surfaces and solids.
Our weights are even more distracting than our long measure. We have in
fact two kinds of weight measure--troy and avoirdupois.