v5 



2 Doniestic Science 



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mearti ?* v>: since all "books do not have pages of the 

 same length. On the other hand, if asked to make 

 a table 6 feet long, he would not make any demur. 



2. Units such as the foot, adopted by common 

 consent, derive their utility from the greater con- 

 venience which arises from their general use. The 

 chief units thus adopted are termed " Standard " 

 units. In the British Isles the standard unit of length 

 is the yard. At the Standards Office of the Board of 

 Trade is kept a bar of bronze with a gold plug near 

 each end. On each plug is engraved a fine transverse 

 line. These lines are parallel to one another, and the 

 legal yard is defined as " the distance between the 

 centres of these lines when the bar is at a temperature 

 of 62 F." (The reason for mentioning the tempera- 

 ture will be understood after reading Chapter VIH.) 

 Accurate copies of the standard are kept in all large 

 towns, and by means of these the correctness of the 

 yard-measures in actual use by tradesmen may be tested. 



3. It usually happens that, when the length of 

 an article is determined by measurement with a yard- 

 measure, its length is not found to be an exact number 

 of yards. Hence yard-measures, tapes, carpenter's 

 rules, and other instruments for measuring length, 

 have marks upon them which divide the measure into 

 a definite number of equal parts. The parts of the 

 yard in common use the foot and the inch are 

 called " submultiples " of the yard. The separate 

 inches are generally subdivided into halves, quarters, 

 eighths, or even smaller fractions of an inch. For 

 measuring lengths which are much greater than the 

 yard, units containing a given number of yards, such 

 as the furlong and mile, are used. These are termed 

 " multiples " of the standard unit. 



