12 



MATTER AND ITS MEASUREMENT 



platinum was substituted for the brass. The English 

 pound weight is still this platinum standard pound. 

 Copies of it, also of platinum, are kept in the United 

 States (Washington) and in other countries. 



The abbreviation "lb.," for "pound/' comes from the Latin libra, 

 or scales. The word " ounce" is probably from unus, "one," and was 

 originally applied to ~h of a pound, as it still is in "Troy" weight. In 

 the form "inch" it was also applied to -fa of a foot. The ton probably 



received its name from ths "tun," a 

 large cask that held about 2,000 pounds 

 of water. 



14. Metric Units of Weight 

 In the metric system the com- 

 mon weight units are the gram 

 and kilogram (1000 grams). A 

 liter of pure water at 4 C. (cf. 

 87) weighs one kilogram. This 

 is abbreviated to "kilo" or to 

 "kg." The international stand- 

 ard kilogram is a piece of plati- 

 num, as is the English standard 

 pound. Forty of these were constructed in Paris, and 

 two of them are in the Bureau of Standards, at Wash- 

 ington (Fig. 12). 



FIG. 12. 

 The Standard Kilogram. 



One cubic centimeter of water, that is, 

 weighs one gram at C. 



of a liter, 



Subdivisions of the gram, like those of the meter, are formed from 

 the prefixes "wuZK," "centi," and "deti." 



