6 JUNIOR GRADE SCIENCE 



possible in the event of the loss of the standard, to replace it by an 

 exact copy. They proposed the one ten-millionth part of the distance 

 from the earth's equator to the pole that is, of the earth's quadrant 

 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 Sevres is arbitrary. An exact copy 

 of this standard is kept in this country ; and for our purposes the 

 metre may be defined as " the length, at the temperature of C., of 

 the iridio-platinum bar, numbered 16, deposited with the Board of 

 Trade." It is equal to 39-37079 inches, or briefly, 3 feet 3-3 inches. 

 The metre is subdivided into ten equal parts, each of which is called a 

 decimetre ; 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 

 10 centimetres) 

 100 millimetres ) 

 10 decimetres "j 

 100 centimetres 1=1 metre 

 1000 millimetres J 



The multiples of the metre are named deka-, hekto-, and kilo-metres. 

 Their value is seen from the following table : 

 1 metres = 1 dekametre 

 100 metres = 1 hektometre 

 1000 metres = 1 kilometre 



The kilometre is equal to about five-eighths of a mile, or eight kilo- 

 metres are equal to five miles. 



3. RATIO OF THE DIAMETER OF A CIRCLE TO 

 ITS CIRCUMFERENCE. 



Measurement of the length of curved lines. All curved lines 

 can be regarded as made up of a very large number of small straight 



FIG. 2. To illustrate how a curve may be considered to be made up of an infinite 

 number of short lines. 



lines. The larger the number of small straight lines intu which we 

 suppose the line to be divided, the more nearly shall we get to the 



