[time-nuts] 15 ns vs. 15 nS

[John Day]

At 10:03 AM 5/22/2007, you wrote:
>Rob Kimberley wrote:
> > Happy memories...
> >
> > I remember being switched half way through my "A" Level Physics course from
> > cgs to MKS in 1968.
> >
> > Legal here in UK to show weights & measures in shops in both metric and
> > imperial systems. Fuel at petrol (gas) 
> stations sold in litres, and distance
> > on roads still shown in miles (!!). Never did understand how the US gallon
> > was smaller than the Imperial one though...
> >
>
>Pretty simple, really, a US gallon is 4 quarts (as in quarters), an imperial
>gallon is 5 quarts.
>
>The real question is when did the imperial gallon pick up the extra quart.

It never did, an Imperial gallon is also four 
quarts, just different quarts! The question 
really is how come the US quart is smaller than 
the Imperial one? The US Gallon has 128 pints, 
the Imperial has 160. The US Gallon is based on 
the Queen Anne gallon of 1706, also known as the 'Wine Gallon'.

Speculating on the US Customary versus Imperial 
systems is a little difficult, as the Imperial 
system wasn't formalised until 1824, by which 
time the former US colonies paid little heed to 
what was going on in England! The Wine Gallon was 
essentially superceded for all purposes except 
the taxing of Wine in 1824, as was the older and 
more commonly used Ale Gallon of about 282 cubic 
inches. They were replaced by the Standard Gallon 
of 277 cubic inches, or more precisely, 10lbs of 
water at 62°F measured in air with brass weights.

So in essence we see two divergent measurement 
systems which didn't converge again until 1852 
(in the case of the nautical mile) and 1959 in 
the case of other units, particularly length. 
Weight, as I recollect, has always been the same. 
some time in the mid-19th century (after the 
standardisation of 1824) the British sent a 
'pound' to the Americans who found it to weight 
the same as their pound. They also sent a couple 
of yards, but there was a slight difference.

In 1893, the BIPM in Paris supplied standard 
metre and kilogramme bars to the US which were 
adopted by the administrative fiat of Thomas 
Mendenhall, Superintendent of Weights and 
Measures in the Treasury Department and they 
thenceforth became the standard for all 
measurements in the US, and since then the US 
customary units have been officially defined in terms of metric units.

John


>-Chuck Harris