CHAPTER II 

 WEIGHTS AND MEASURES 



10. Units of Measure. Since not all objects have the 

 same dimensions, it becomes necessary to have standards 

 with which different bodies may be compared. The three 

 fundamental units that are used in our daily experiences 

 are the units of time, length, and mass. Without these units 

 it would be impossible to do accurate work or to give and 

 receive working instructions. 



The unit of time is the second and is the same in all coun- 

 tries. The day is divided into 24 hours of 60 minutes each, 

 and each minute contains 60 seconds. Twenty-four hours, or 

 one day, is the time taken by the earth to make onecompfete 

 revolution on its axis. In most trades the hour, minute, 

 and second are used in place of the day as the practical 

 working units of time. 



The unit of length by means of which the English-speaking 

 races measure distance is the yard. The standard of length 

 in the British system is the imperial yard. It was defined 

 by an act of Parliament in 1855 as the distance between two 

 cross lines in two gold plugs in a certain bronze bar, kept at 

 62 Fahrenheit. This bar is preserved at the Board of 

 Trade office in London. Though the unit of length was 

 intended to be the same for England and America, in reality 

 the United States yard exceeds the British by .00087 of an 

 inch. The United States standard yard is the distance 

 between the twenty-seventh and sixty-third inch marks 



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