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From: msb@dciem.UUCP (Mark Brader)
Newsgroups: net.misc,net.games.trivia
Subject: Re: Measurements
Message-ID: <1939@dciem.UUCP>
Date: Thu, 28-Aug-86 20:06:06 EDT
Article-I.D.: dciem.1939
Posted: Thu Aug 28 20:06:06 1986
Date-Received: Thu, 28-Aug-86 21:40:38 EDT
References: <740@moscom.UUCP> <2133@orca.UUCP> <627@hropus.UUCP> <6016@fortune.UUCP>
Reply-To: msb@dciem.UUCP (Mark Brader)
Organization: NTT Systems Inc., c/o DCIEM, Toronto
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Xref: dciem net.misc:8278 net.games.trivia:2305
Summary: 

There is lots to say about this, but I will confine myself to a few points.
If you want to find more, go to your library and read all about it!

> One ml or cc (they are not the same, by 24 parts
> per million, I don't remember which one's larger) of water at 4 degrees
> weighs 1 gram.

Nope.  The original idea, of course, was that 1 ml = 1 cc = volume of 1 g
of water at maximum density; and then when the standards were found to be
not quite equal, it was resolved my making 1 ml = volume of 1 g of water
under appropriate conditions and 1 cc slightly different.  However, about
20 years ago the ml was CHANGED and it is now equal to the cc.  So the
density of water at 4 C is not exactly 1 g/ml any more.

By the way, cc is bad notation; it should be written cm-superscript-3.
But that does look lousy on terminals.

> One fluid ounce of water is 29.57 ml, one ounce weighs
> 28.35 grams.  So one fluid ounce weighs 1.043 ounces.

Correct (to the stated accuracy).  However, one British (Imperial) fluid ounce
is 28.41 ml, and thus weighs just over 1.002 ounces.

] And don't forget that a British pint (whence I assume the word 'pint'
] originated) has 20 fluid ounces in it!

And therefore a British gallon has 160 fluid ounces, and a British gallon
of water weighs 10.02+ pounds.  Undoubtedly it was supposed to be 10 pounds
exactly, but a similar situation to the ml-vs-cc developed, and the same
ultimate resolution was chosen.	

See, the US system has the advantage of keeping everything in powers of 2,
with the gallon of 128 fl.oz., but the British system makes a gallon of
water near a round weight, and a fluid ounce of water near an ounce.
So each system has an advantage.

Incidentally, in the U.S. system a gallon is exactly 231 cubic inches.
As far as I can tell, this is arbitrary.  The British gallon is probably
defined in metric now, but used to be defined by an object.  Note that
the British and U.S. gallons are in the ratio 1.201-; anyone who gives
the ratio as 1.25 is thinking the two fluid ounces are equal.

By the way, while Canada the British measures in this series, we use the
American or short ton (when we don't use metric in each case).  The British
or long ton of 2240 pounds is, of course, 20 hundredweights of 8 stones of
14 pounds; the short ton (and short hundredweight) presumably arose by round-
ing.  Stones are still in everyday use in Britain.  I don't know about any
connection of ton and tun, but as for the metric ton or tonne, it is just
a more pronounceable synonym for megagram (Mg), arising because of its
similarity at 2205- pounds to one or more of the others.

The avoirdupois (ordinary) pound, on which the British volume measures
seem to be based, also arose by rounding.  The Troy and apothecaries'
pound of 12 ounces of 480 grains is older.  However, someone decided
that 16 ounces to the pound would be more convenient, but then decided
that 7680 grains to the pound wouldn't be convenient and rounded it down
to 7000, so the avoirdupois ounce is 175/192 of the troy/apothecaries\ ounce.

What's even weirder is that in British volume measure the fluid ounce is
equal to 8 fluid drams (or drachms) (which I don't think are used any more
anyway), just as in apothecaries' weight the ounce is 8 drams, but NOT as
in avoirdupois weight on which the volume system is based, because in
avoirdupois weight the ounce is 16 drams!  So one British fluid dram of
of water weighs just about 2 avoirdupois drams.

As for pints and pounds, my suspicion is that the phrase arose in Britain
in an older era when the two kinds of gallon (and others, I think) were
still competing there, and stuck by reason of euphony.  But I'm guessing.

Mark Brader	  "I'm not a lawyer, but I'm pedantic and that's just as good."
utzoo!dciem!msb						       -- D Gary Grady