Pounds and Ounces
Pounds and ounces, or imperial measurements as they were known, were used until 2000 in UK shops. One pound was abbreviated to lb, from the Latin word libra. There were sixteen ounces in a pound and the abbreviation was oz.
The system was known as avoirdupois. It does not translate directly from modern French, as 'avoir du pois' literally means 'to have peas'. However, the term came from the old French expression 'aveir de peis' and meant 'goods of weight'. 
Weight measurements under the avoirdupois system are:
- 16 drams = 1 ounce (1 oz)
- 16 ounces = 1 pound (1 lb)
- 14 pounds = 1 stone
- 112 pounds = 1 hundredweight (1 cwt)
- 20 hundredweight = 1 ton
There were also 7000 grains in a pound.
- 8 pounds = 1 butcher's stone (used in London meat markets)
- 100 pounds = 1 central or new hundredweight
There was also a quantity known as a bushel.
A bushel was the volume of 80 lb of distilled water. It had a volume of 2219.192 cubic inches .
Bushels of different comodities had different weights:
- A bushel of apples weighed 40 lb
- A bushel of patotoes weighed 56 lb
- A bushel of salt weighed 56 lb
- A bushel of peas weighed 63 lb
- A bushel of coal weighed 80 lb
A bushel was sub-divided into 4 pecks.
People used troy weights for measures of precious metals such as gold. They were not well understood by most people.
They have no connection with the ancient City of Troy, but instead the French town of Troyes, which was known in medieval times for its commercial fairs. 
Troy weights are as follows:
- 3.17 grains = 1 carat
- 24 grains = 1 pennyweight (dwt)
- 20 pennyweights = 1 ounce (or 480 grains)
- 12 ounces = 1 pound (or 5,760 grains)
- 100 pounds = 1 hundredweight
Troy ounces, pounds and hundredweights are not the same as avoirdupois ounces, pounds and hundredweights. However, grains are. So 1 troy grain is equal to 1 avoirdupois grain.
You can see from the above that 1 troy pound is 12 x 20 pennyweights or 240 pennyweights. There are 240 old pennies in a pound. Is there a connection?
The answer is, yes, the first money pound was 240 silver pennies. Each penny was supposed to weigh a pennyweight so a £ in money was also a pound in weight. However, the Mint used what was called the tower pound instead of the troy pound. The tower pound was so called because the Mint was in the Tower of London. A tower pound was 15 sixteenths of a troy pound and a tower pennyweight was in proportion. 
Apothecaries' weights were used by chemists and doctors for medical preparations.
- 20 grains = 1 scruple
- 3 scruples = 1 drachm
- 8 drachms = 1 ounce (480 grains)
- 12 ounces = 1 pound
Apothecaries' ounces and pounds are the same as troy ounces and pounds.
Law's Grocery Manual noted that the apothecaries' weights were 'old'. They were discontinued in the UK by the Medical Act, 1858. From then onwards, avoirdupois weights were to be used in medicines 
|20 fl.oz (fluid ounces) = 1 pint|
|8 pints = 1 gallon|
|12" (inches) = 1' (foot or ft)|
|3 feet = 1 yard (yd)|
|1760 yards = 1 mile|
 - source Law's Grocery Manual, fourth edition, published 1949
 - Thomas Snelling, A View of the Silver Coin and Coinage of England, from the Norman Conquest to the Present Time, Consider'd with Regard to Type, Legend, Sorts, Rarity, Weight, Fineness and Value : with Copper Plates, published 1762
 - François Cardarelli, Encyclopaedia of Scientific Units, Weights and Measures: Their SI Equivalences and Origins, Revised edition published 2003, page 38
 - Third report of the Commissioners appointed to inquire into the condition of the Exchequer (now Board of Trade) Standards on the abolishion of Troy weeight, published by Her Majesty's Stationary Office, 1870.
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