2. Texts Measurments and Weights

2.2.1 Read the texts and explain what the difference is between the British Imperial System and the u.S. One.

The British Imperial System

The British system of weights and measures has evolved from units having many origins, many of the units having been introduced into Britain at the time of the Roman conquest.

The basic units of the British imperial system are the Yard, the Pound, and the Gallon.

The British imperial yard is defined (Weights and Measures Act, 1878) as the distance, at 62.00°F., between two fine lines engraved on gold studs sunk in a specified bronze bar known as “№ 1 stand­ard yard.” This bar was cast in 1845.

The British imperial pound is defined as the mass (the weight in vacuo) of a cylinder of pure platinum about 1.35 in. high and 1.15 in. diameter. This is the only pound legal for use in Great Britain and is sometimes called the avoirdupois pound.

The British imperial gallon is the volume of 10 lb. avoirdupois of pure water as weighed in air against brass weights, the temperature of the air and the water being 62 °F., and the barometric pressure 30 in. of mercury. This legal definition is incomplete; for instance it does not state the density of the brass weights, but in official comparisons this density is taken as 8.143 g. per cm".

The multiples and subtnultiples of the British yard are similar to the corresponding units of the U.S. customary system. It is subdi­vided into 3 feet of 12 inches each. Five and a half yards (16 1/2 ft.) make a rod, pole, or perch. 40 rods make a furlong; and 8 furlongs (5,280 ft.) make a statute mile. Units of area and volume are simply the squares and cubes, respectively, of the units of length, except for the insertion of the acre which consists of 43,560 square feet.

The British pound is subdivided into16 ounces, or 256 drams, or 7,000 grains. Fourteen pounds equal 1 stone, 2 stones = 1 quarter (28 pounds), 8 stones =1 hundredweight (cwt) = 112 pounds, and 20 hundredweight = 1 ton = 2,240 pounds. This ton (i. e. of 2,240 pounds) is called gross ton or long ton to distinguish it from the net ton or short ton which is equal to 2,000 pounds.

The British gallon, as defined above, is by calculation equivalent to 277.42 cubic inches. It is used as a unit of capacity, both liquid and dry.

The British gallon is divided into 4 quarts, or 8 pints, or 32 gills, or 160 fluid ounces (the U.S. gallon being divided into 128 fluid ounces, the result is that the British fluid ounce is smaller than the U.S. fluid ounce, whereas the other British units of capacity are larg­er than the corresponding U.S. units). Two gallons make a peck, 8 gallons make a bushel, and 8 bushels make a quarter.

The U.S. Customary system

The weights and measures in common use in the American colonies at the time of the American Revolution were all of English origin and were the same as those then used in Great Britain.

The following unils are still in use in the United States: (a) the yard of 35 inches, (b) the avoirdupois pound of 7,000 grains, (c) the gallon of 231 cubic inches, and (d) the winchester bushel (or simply bushel) of 2,150.42 cubic inches.

In 1893, after receipt of the metric standards, it was decided that a more stable basis for the system of customary weights and measures in the United States would be obtained by defining the yard in terms of the metre and the pound in terms of the kilogram using the U.S. prototype metre and the U.S. prototype kilogram, respectively, with their certified corrections as the primary standards of length and mass in this country. This is the present basis of the units.

The U.S. yard is defined as 3.600/3.937 metre and the U.S. pound as 0.4535924277 kilogram.

For industrial purposes, in the conversion of inches to millimetres and millimetres to inches, a relation between the inch and the millimetre has been adopted by the American Standard Association (1933) and by similar organizations in other countries.

This relation is

1 inch = 25.4 millimetres (exactly)

whereas the relation 1 U.S. yard = 3.600/3.937 = metre gives

1 inch = 25.4000508 millimetres.

It is to be noted that although the mass of a body, often de­fined as the quantity of matter in a body, remains constant everywhere and under all conditions as long as no portion of the body is taken away and no matter added to it, its weight, being a force equal to the product of mass of the body by the acceleration of gravity, varies with the locality in which it is measured.