Comments on: Metric, a truly natural system

by: richard

Sat, 16 Aug 2008 11:33:02 +0000

Elsewhere, you’ve suggested USA is not metric…… Well, try this reference:
http://lamar.colostate.edu/~hillger/laws/metric-conv.html
and Wikipedia too:
http://en.wikipedia.org/wiki/Metrication_in_the_United_States
And I’ve seen metric speed signs in Hawaii.

So they are even more confused than UK.

by: philh

Wed, 18 Jun 2008 16:28:31 +0000

Thank you Martin for the correction. I take it that your contribution was intended to show that the origin of the pound weight is even more obscure than I was suggesting.

by: Martin Vlietstra

Wed, 18 Jun 2008 07:52:15 +0000

It is a myth that the pound weight is related to a pound in coinage. Precious metals and medicines used to be measured in Troy units, but other commodities in Avoirdupois units. One Troy pound (12 Troy ounces) was defined to be 5760 grains while a pound Avoirdupois (16 ounces Avoirdupois) was 7000 grains. A pennyweight (Troy units) was 24 grains which is 1/240 of a Troy pound and was the weight of a silver Anglo-Saxon penny.

The pennyweight and Troy pound ceased to have a legal status in the UK in 1878, but the Troy ounce may still be used legally for the sale of precious metals.

For the record
1 troy pound = 373.24g
1 troy ounce = 31.103 g
1 pennyweight = 1.555 g

1 pound avoirdupois = 453.59 g
1 ounce avoirdupois = 28.35 g

1 grain = 64.80 mg