

CHAPTER II 



UNITS OF LENGTH, AREA AND VOLUME 



Measurement of Length. We have from time to time in 

 the preceding chapter referred to lengths as being of so many 

 yards, or feet, or centimetres, and it is desirable, before going 

 further, to acquaint the student with the exact significance of 

 these and other measures of length. It is clear that before 

 comparing any one length with any other we must have some 

 standard to which we can refer them. In this country the 

 standard adopted is the length between two marks on a platinum 

 bar kept at the Exchequer Chambers, the bar being at a certain 

 fixed temperature when the measurement is made. This length 

 is quite arbitrary and is called a yard. The yard is subdivided 

 into three equal parts, each of which is a foot. The foot is in 

 its turn divided into twelve equal parts, called inches. Multiples 

 of the yard are also used and special names given to them, 

 thus : 



2 yards = 1 fathom. 



5| yards = 1 rod, pole, or perch, 



40 poles = 1 furlong. 



8 furlongs) _ ^ n 

 1,760 yards \ 



We have given these in full to show how clumsy and unsatis- 

 factory the British measures of length are, and to point out 

 that it is for this reason they are not used in scientific work, 

 even by British men of science. 



French geometricians decided that such an arbitrary standard 

 was, in view of the chance of its loss or destruction, an undesir- 

 able one, and suggested that if a fraction of the circumference 

 of the earth were taken they would, in the event of the loss of 



