22 ELEMENTARY GENERAL SCIENCE CHAP. 



the standard, be easily able to replace it by an exact copy. 

 They proposed the one ten millionth part of the earth's 

 quadrant, i.e., of the distance from the equator to the pole, as a 

 suitable length, and this they called the metre. After bars had 

 been prepared of this length it was unfortunately 

 found that the length of the quadrant had not 

 been exactly determined, and consequently the 

 length of the standard metre at Paris is arbitrary, 

 and we must define the standard metre as being 

 the length at a certain temperature between two 

 marks on a platinum bar kept at Paris. It is equal 

 to 39'37079 inches. The metre is subdivided into 

 ten equal parts, each of which is called a deci- 

 metre, the tenth part of the decimetre is called a 

 centimetre, and the tenth part of the centimetre 

 is known as a millimetre. Thus we get 



10 millimetres = 1 centimetre. 



o 10 centimetres 



100 millimetres 



^ 



~ 10 decimetres 



= 1 decimetre. 



100 centimetres !- =1 metre. 

 1,000 millimetres J 



2 



The multiples of the metre are named deka-, 



hecto-, and kilometres. Their value is seen from 

 the following table : 



10 metres = 1 dekametre 

 100 metres = 1 hectometre 

 1,000 metres = 1 kilometre 



The kilometre is equal to about three- fifths of a 

 mile. 



Exercises in Linear Measurement. EXPT. 

 25. Procure a rule divided into inches and parts of an inch 

 on one edge, and centimetres and parts of a centimetre 

 on the other. 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. 



