THE MEASUREMENT OF MATTER 35 



waves are unvarying and the exact length of a meter can, 

 therefore, be found at any time. 



39. Divisions of the Metric S/stem. The meter is divided 

 into tenths (decimeters), hundredths (centimeters), and thou- 

 sandths (millimeters), the names of these divisions being made 

 by using the Latin prefixes deci (10) centi (100), and milli 

 (1000). The words dime, cent, and mill in our coinage have 

 the same significance. Multiples of the meter have names 

 made by using the Greek prefixes. Thus ten meters is a deka- 

 meter, one hundred meters a hectometer, and one thousand 

 meters a kilometer. Of these larger divisions, the kilometer is 

 the only one commonly used, smaller lengths being expressed 

 in meters or its divisions, especially centimeters and milli- 



CENTIMETER 



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INCH 1 2 3 



FIG. 6. Centimeter and inch scales. (Tower, Smith and Turton.} 



meters. In the measurement of surfaces, since two dimen- 

 sions are involved, one hundred (10 X 10) of one division 

 makes one of the next. Thus 100 square centimeters makes 

 a square decimeter, and 100 square decimeters makes a square 

 meter. 



40. Grams and Liters. The unit of weight in the metric 

 system is designated as the weight of a cubic centimeter of 

 pure water at its greatest density (4C.). This unit is called 

 the gram. We can get some idea of the weight of a gram by 

 remembering that our five-cent coin or nickel weighs five 

 grams. Like the meter, the gram is divided into tenths, 

 hundredths, and thousandths, and the names of the divisions 

 are formed by using the same prefixes. A thousandth of a 

 gram, therefore, is a milligram and a thousand grams is a kilo- 



