The traditional poundas a unit of weight was used throughout the Roman
Empire. But like many other measurements over time, the number of ounces in a
pound seemed to shift and change. For example, the number of ounces in the Roman
pound was 12; European merchants used 16 ounces to the pound. Eventually, 16
ounces in a pound became standard (for more about ounces, see below).
Back in the 19th century, the Americans—who did not like the British larger
weights—decided that a hundredweight would equal 100 pounds (the British hun-
dredweight was 112). This meant a ton was equal to 20 hundredweight for the Ameri-
can ton (or the American’s short tonwas 2,000 pounds), while the British long tonof
20 hundredweight was equal to 2,240 pounds. There were, of course, debates, but not
everyone disagreed with the American short ton. It became the favorite of British mer-
chants, who called it a cental. Eventually, the ton on the international market “went
metric,” and today a metric tonis close to the original British long ton. It is equal to
1,000 kilograms, or approximately 2,204 pounds, and is officially called a tonne.
Although the International System (SI; see p. 50) standard uses tonne, the United
States government recommends using the metric ton.
Where did the pound(and its abbreviation, “lb.”) originate?
The origin of the word “pound” comes from libra pondo,or “pound of weight.” The
common abbreviation for pound (lb.) originated from letters in the Latin word libra,
or balanced scales.
What is the difference between the various poundsand ounces?
The story behind the ounce is long and convoluted because historically people have
been dissatisfied with the unit. For example, in medieval times English merchants 47
MATHEMATICS THROUGHOUT HISTORY
Why was the troy pound so
historically important to weight measurement?O
ne of the oldest English weight systems was based on the 12-ounce troy
pound. It was the basis by which coins were minted, and gold and silver
weighed for trade and commerce. (The troy pound equaled 5,760 grains, and thus,
in ounces, was 5,760/12 or 480 grains; 20 pennies weighed an ounce, and thus, a
pennyweight equaled 480/20 or 24 grains.) The troy pound—and the entire system
of connected weights—was used until the 19th century, mostly by jewelers and
druggists. One holdover of the troy ounce (a portion of the troy pound) is found in
today’s pharmaceutical market to measure certain drugs. It is also seen in the
financial markets, where it is used to interpret gold and silver prices.