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Formulas
& Conversion tables
A Brief History
of Measurement
by Frank Tapson www.a
dictionary of units
One of the earliest types of measurement concerned that of
length. These measurements were usually based on parts of
the body. A well documented example (the first) is the Egyptian
cubit which was derived from the length of the arm from the
elbow to the outstretched finger tips. By 2500 BC this had
been standardised in a royal master cubit made of black marble
(about 52 cm). This cubit was divided into 28 digits (roughly
a finger width) which could be further divided into fractional
parts, the smallest of these being only just over a millimetre.
In England units of measurement were not properly standardised
until the 13th century, though variations (and abuses) continued
until long after that. For example, there were three different
gallons (ale, wine and corn) up until 1824 when the gallon
was standardised.
In the U S A the system of weights and measured first adopted
was that of the English, though a few differences came in
when decisions were made at the time of standardisation in
1836. For instance, the wine-gallon of 231 cubic inches was
used instead of the English one (as defined in 1824) of about
277 cubic inches. The U S A also took as their standard of
dry measure the old Winchester bushel of 2150.42 cubic inches,
which gave a dry gallon of nearly 269 cubic inches.
Even as late as the middle of the 20th century there were
some differences in UK and US measures which were nominally
the same. The UK inch measured 2.53998 cm while the US inch
was 2.540005 cm. Both were standardised at 2.54 cm in July
1959, though the U S continued to use 'their' value for several
years in land surveying work - this too is slowly being metricated.
In France the metric system officially started in June 1799
with the declared intent of being 'For all people, for all
time'. The unit of length was the metre which was defined
as being one ten-millionth part of a quarter of the earth's
circumference. The production of this standard required a
very careful survey to be done which took several years. However,
as more accurate instruments became available so the 'exactness'
of the standard was called into question. Later efforts were
directed at finding some absolute standard based on an observable
physical phenomenon. Over two centuries this developed into
the S I. So maybe their original slogan was more correct than
anyone could have foreseen then.
Gallons to Litres
To convert imperial gallons to litres, multiply by 4.55
To convert litres to imperial gallons, multiply by 0.22
US gallons to litres, multiply by 3.79
Litres to US gallons, multiply by 0.26
Calculating the flow of water in a
culvert
Soon.
Finding the Volume of a Tank, a selection
of answers from the Dr. Math archives.
Dr
Math tank volumes
For more detailed answers of questions such as:
Liquid in an Elliptical Tank
Sorry.
More will be coming soon.
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