Weights and Measures Act 1985

SCHEDULE 2 U.K. Existing United Kingdom Primary Standards andAuthorised Copies

Part I U.K. Description of United Kingdom primary standard of the yard

A solid bronze bar, about 38 inches long and about 1 inch square in transverse section, marked “Copper 16 oz. Tin 2½ Zinc 1 Mr. Baily’s Metal No. 1 STANDARD YARD at 62°·00 Faht. Cast in 1845 Troughton & Simms, LONDON.” and having near to each end a cylindrical hole sunk to the depth of about½ inch at the bottom of which is inserted in a smaller hole a golden plug about one-tenth of an inch in diameter with, cut upon its surface, three fine lines about one hundredth of an inch apart transverse, and two fine lines about three hundredths of an inch apart parallel, to the axis of the bar, measurement being made of the mean interval between the two plugs on their respective middle transverse lines between their respective longitudinal lines when the bar is at the temperature of 62° Fahrenheit and supported on bronze rollers placed under it in such manner as best to avoid flexure of the bar and to facilitate its free expansion and contraction from variations of temperature.

Part II U.K. Description of United Kingdom primary standard of the pound

A platinum cylinder about 1.35 inches in height and about 1.15 inches in diameter marked “PS 1844 1 lb”, having its edges rounded off and a groove about 0.34 inch below the top of the cylinder.

Part III U.K. Description of United Kingdom primary standard of the metre

The British copy of the prototype metre, being a bar about 102 centimetres long with a cross-section of modified X-form and made of platinum-iridium alloy (90 per cent. platinum, 10 per cent. iridium), bearing at one end the markings “0°C & 20°C”, “A.16 SIP GENEVE 1956” and (on the cross-section) “1” and at the other end the markings “B.16” and (on the cross-section) “2”, and having engraved on the exposed neutral plane—

(a) near each end and also at the centre, two parallel longitudinal lines about 0.12 millimetre apart;

(b) near the end marked “1” and at the centre, one transverse line; and

(c) near the end marked “2”, two transverse lines about 0.17 millimetre apart,

measurement being made of the mean interval between the portions of the most widely separated transverse lines which are between the respective longitudinal lines when the bar is at the temperature of 0° Celsius, is subjected to an atmospheric pressure of 1013.250 millibars, and is supported on two rollers at least one centimetre in diameter placed symmetrically 571 millimetres apart in the same horizontal plane.

Part IV U.K. Description of United Kingdom primary standard of the kilogram

The British copy of the prototype kilogram, being a solid cylinder marked “18” of height equal to its diameter made of platinum-iridium alloy (90 per cent. platinum, 10 per cent. iridium).

Part V U.K. Authorised copies of United Kingdom primary standards of the yard and pound

Copies of the bar and cylinder described in Parts I and II respectively of this Schedule of the same construction and as that bar and cylinder are respectively marked and deposited as follows—

(a) a bronze bar marked “Copper 16 oz. Tin 2½ Zinc 1 Mr. Baily’s Metal No. 2 STANDARD YARD at 61°·94 Faht. Cast in 1845 Troughton & Simms, LONDON.”, and a platinum cylinder marked “No. 1 PC 1844 1 lb”, deposited at the Royal Mint;

(b) a bronze bar marked “Copper 16 oz. Tin 2½ Zinc 1 Mr. Baily’s Metal No. 3 STANDARD YARD at 62°·10 Faht. Cast in 1845 Troughton & Simms, LONDON.”, and a platinum cylinder marked “No. 2 PC 18441 lb”, deposited at the premises of the Royal Society;

(c) a bronze bar marked “Copper 16 oz. Tin 2½ Zinc 1 Mr. Baily’s Metal No. 5 STANDARD YARD at 62°·16 Faht. Cast in 1845 Troughton & Simms, LONDON.”, and a platinum cylinder marked “No. 3 PC 1844 1 lb”, deposited at the Royal Greenwich Observatory;

(d) a bronze bar marked “Copper 16 oz. Tin 2½ Zinc 1 Mr. Baily’s Metal No, 4 STANDARD YARD at 61°·98 Faht. Cast in 1845 Troughton & Simms, LONDON.”, and a platinum cylinder marked “No. 4 PC 18441 lb”, immured in the Palace of Westminster;

(e) a bronze bar marked “Copper 16 oz. Tin 2½ inc 1. BAILY’S METAL. PARLIAMENTARY COPY (VI) OF THE IMPERIAL STANDARD YARD. 41 & 42 VICTORIA, CHAPTER 49. STANDARD YARD AT 62° FAHT. CAST IN 1878. Troughton & Simms. London. H.J.C.”, and a platinum-iridium cylinder marked “P.C. 5 1879” deposited at the National Weights and Measures Laboratory of the Department of Trade and Industry.