Why are there three types of Gallons?
There are imperial gallons, US gallons and, something I just learned
on GA, even "fluid" gallons?

Why three?

Auggh! The virtues of the metric system are very clear when one starts
fiddling around with these archaic units of measure.

The measurement of popular alcoholic beverages in bygone times led to
different standards on the two sides of the Atlantic. The Imperial
gallon (still used in the UK for certain commodities) is based upon an
old measure called the "ale gallon," while the US gallon is based upon
an old measure called the "wine gallon." So it could be said that the
beverage preferences of the US and Britain are responsible for the
schism.

The Imperial gallon is customarily used for both dry and liquid
commodities. However, in the United States, another instance of
measurement madness has given us the "fluid gallon" as a standard for
measuring liquids.

"According to "The International System of Units: Physical Constants and
Conversion Factors"  published by NASA in 1966...

One U.S. dry gallon is 4.40488377086 liters.
One U.S. fluid gallon is 3.785411784 liters.
One British gallon is 4.546087 liters (approximately, not a definition)."

Homebrew Digest
http://hbd.org/hbd/archive/530.html

"At one time, the volume of a gallon depended on what you were
measuring, and where you were measuring it. But, by the 19th century,
two definitions were in common use. The wine gallon, which was 231
cubic inches, and the ale gallon, of 282 cubic inches.

In 1824, Britain adopted a close approximation to the ale gallon known
as the Imperial gallon. The Imperial gallon is based on the volume of
10 pounds of distilled water weighed in air with the barometer
standing at 30 inches and at a temperature of 62 degrees Fahrenheit
(and in 1963 this definition was refined as the space occupied by 10
pounds of distilled water of density 0.998859 g/ml weighed in air of
density 0.001217 g/ml against weights of density 8.136 g/ml). This
works out at 277.41945 cubic inches.

The United States by this time, had already standardised on a close
approximation to the old wine gallon. It was at one time defined as
the volume of a cylinder 6 inches long and 7 inches in diameter, or
230.907 cubic inches. Today, however, the gallon is 231 cu. ins
exactly. Thus 10 US gallons equals 8.327 Imperial gallons. The
Imperial gallon is about a fifth larger than the US gallon.

Both the Imperial and United States gallon are equal to 8 pints.
However in the US a pint is 16 fluid ounces whereas an Imperial pint
is 20 fluid ounces. Thus a U.S. gallon is 128 fl. oz and an Imperial
gallon is 160 fl. oz; this means that a US fluid ounce is around
1.8047 cu. ins and an Imperial fl. oz is around 1.7339 cu. ins. The US
fluid ounce is actually bigger than the imperial, although the US
gallon is smaller."

Science Fair Projects Encyclopedia: Gallon
http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Gallon

"The origins of these differences lie in the variety of systems that
were in use in Britain at the time of the establishment of the first
colonies in North America. The American colonists adopted the English
wine gallon of 231 cubic inches, and used it for all fluid purposes.
The English of that period used this wine gallon, but they also had
another gallon, the ale gallon of 282 cubic inches. In 1824, the
British abandoned these two gallons when they adopted the British
Imperial gallon, which they defined as the volume of 10 pounds of
water, at a temperature of 62 °F, which, by calculation, is equivalent
to about 277.42 cubic inches (4,546 cm³)- much closer to the ale
gallon than the wine gallon. At the same time, they redefined the
bushel as 8 gallons.

...in the customary British system the units of dry measure are the
same as those of liquid measure. In the United States these two are
not the same, the gallon and its subdivisions are used in the
measurement of liquids; the bushel, with its subdivisions, is used in
the measurement of certain dry commodities. The U.S. gallon (3.785 411
784 L) is divided into four liquid quarts (946.352 946 mL each) and
the U.S. bushel (35.239 070 166 88 L) into 32 dry quarts (1.101 220
942 715 L each) or 4 pecks (8.809 767 541 72 L each). All the units of
capacity or volume mentioned thus far are larger in the customary
British system than in the U.S. system. But the British fluid ounce is
smaller than (about 96% of) the U.S. fluid ounce, because the British
quart is divided into 40 fluid ounces whereas the U.S. quart is
divided into 32 fluid ounces."

Wikipedia: Imperial Units
http://en.wikipedia.org/wiki/Imperial_unit

Google search strategy:

Google Web Search: "fluid gallon" "imperial gallon"
://www.google.com/search?hl=en&q=%22fluid+gallon%22+%22imperial+gallon%22

I'm sorry I can't give a more easily understood answer, but when the
facts are so lacking in intelligibility, there isn't any way to
simplify them. This could be one of the few times when your "Request
Clarification" button may not be much use, but let me know if there's
anything further I can do.

Now, where is that "Request Obfuscation" button? :-D
 
Best,
Pink

How many pecks of corn does it it take to make a liquid quart of corn whiskey?
Never mind :)
Thanks for clearing it up Pink.

This clearly refutes the Texans' claim that everything there is bigger.

Hey, don't knock the Imperial measurements. There's a romance to pecks
and bushels and stones that simply isn't matched by the gram or the
liter. The important thing is to have some absolute measure of mass
and distance, and not to force all nations to count with the same
multiples. There's nothing intrinsically good or necessary about the
metric system.

Consider how much more good it does the mind to work in fractions with
varying denominators than to manipulate boring old powers of ten. In
the days of shillings and crowns, every schoolboy who wished to buy a
packet of sweets was inducted into the workings of mixed fractions.
The British intellect is all the poorer for the demise of the
shilling.

leapinglizard

GRT, Pink, Probo, Leaping One,

Concur, concur in favour of old
Ten Gallon Hats reside in Texas
Romance sustained Imperial
Equations are meant to vex us

Bushels to pecks and stones to ounce
Shillings, Pence, miles and yards
"Centimetering up the cliff face"
Not quite the words of bards

"Inching away from death"
Now thats the talk of danger
Furlongs, Chains and Acres
Surely, metric is the stranger

Quids, bobs, zacs and deeners
Tuppence to the paper boy
Poetry is the Imperial
Lending romantic meaning of joy

To uncharted shores of New Holland
The English Guinea deported the Quid
Convicts offered free pardon
Redeemed payment for discretions "did"

Over two hundred years have surpassed
Yet to my own delights
Apart from my origin, Irish
My reference in measure incites

I still refer to miles
Yards and pounds and feet
The way of the poet is that of old
Imperial .. hard to beat

Phil

Wow, thanks for five stars and the nine-gallon tip! 

As for the corn whiskey question, I might be able to answer that, but
then the revenooers would come outta the woods and clobber my still,
and there goes my livelihood. ;-)

~Pink

Would any of you romantics care to calculate the number of cubic
inches in a cubic light year? Assuming ten trillion = 10E12 kilometers
per light year. 10E36 cubic kilometers = 10E45 cubic meters = 10E51
cubic centimeters. It is much easer to then convert cubic centimeters
to cubic inches, 16.4 cubic centimeters per cubic inch.  Neil

Q. What's the difference between an amateur computer person and a professional.

A  An amateur thinks that there are 1000 metres in a kilometer and a  
  professional knows that there are 1024.

Why should we go for any metrication system that has convenient
factors when God gave us all ten fingers and ten toes? It was
evidently meant to be. So from 2010 I?m proposing that we all adopt
the ten month year.
We could also have the ten day week with a three day weekend. It then
follows that we have a ten hour day with a hundred minutes in each
hour and a hundred seconds in each minute. Who in their right mind
would invent a counting system with a base of 365.25 in the first
place? The metrication board would have to find a way of putting the
earth into an orbit of exactly 250 days, which would mean we would all
live longer but get older quicker and I could move into the birthday
card business.

Everyone for this one raise their hands now.

Oh! I thought I would have a better response than that.

Capitaineformidable.

I strongly object to capitaineformidable-ga's proposal for a 10-month year, etc.

Birthdays, Tax Returns & Christmas come along quite fast enough already, thank you.

Now a 100-month year makes a lot of sense, provided income is
pro-rated to ye olde system.