MEASUREMENT OF LENGTH 5 



iv. Metric measures of length. (a) Look at a rule divided into inches 

 and parts of an inch on one edge, and metric measures on the other, as in 

 Fig. 1. The smallest divisions upon the metric scale are millimetres (mm.) ; 

 10 of these millimetres make 1 centimetre (cm.), 10 centimetres make a 

 decimetre (dm.), and 10 decimetres make 1 metre. A metre thus contains 

 10 decimetres, 100 centimetres, and 1000 millimetres. 



(6) Find how many millimetres there are in the length of this page. 

 Write down the result in (1) millimetres, (2) centimetres and tenths of a 

 centimetre, (3) decimetre and tenths and hundredths of a decimetre. 



v. Relation between Metric and British measures of length. (a) Measure 

 the length of this page both in inches and centimetres ; also determine 

 other lengths in the two systems of measurement. 



Put down the results in parallel columns, as shown below, and from them 

 calculate the number of centimetres in an inch. 



(6) Upon the back of an ordinary tape measure, mark off a length equal 

 to 100 centimetres, that is, 1 metre, starting from the point where the 

 inches begin on the other side. Prick a hole through the measure at the 

 point where you mark the length of a metre, then turn over the measure 

 and notice where the hole occurs on the inch scale. 



Number of inches in one metre =39' 3. 



Number of centimetres in one yard = 91 -4. 



British measures of length. To secure uniformity, and provide a 

 permanent length with which others may be compared if necessary, 

 a standard of length has to be agreed upon, and this has been described 

 as follows in a publication of the Standard Department of the Board 

 of Trade : "In the Imperial system of measures the yard is the unit 

 of length, and from this measure are derived all other measures of 

 extension based on that system, whether linear, superficial, or solid. 

 It is represented by the distance between two fine lines traced on a 

 metal bar which is deposited with the Board of Trade. This bar is 

 made of bronze or gun metal ; it is 38 inches long, and one square 

 inch in section, the defining lines being traced on gold plugs or pins 

 inserted at the bottom of a cylindrical hole near to each end of the bar." 



Metric measures of length. When new standards of measurement 

 were being considered in France, in 1795, French geometricians decided 

 that an arbitrary standard such as our yard, in view of the chance of 

 its loss or destruction, was undesirable, and they suggested that if a 

 fraction of the circumference of the earth were taken, it would be 



