ARITHMETIC 297 



MEASURES OF ANGLES OR ARCS 



CIRCULAR MEASURE 



60 seconds (*) =1 minute ' 



60 minutes =1 degree 



360 degrees =1 circle 



60"= 1' 



3,600*= 60'= 1 

 1,296,000 / ' = 21,600' = 360=10 



A quadrant is one-fourth of a circle, or 90; a sextant is 

 one-sixth of a circle, or 60. A right angle (L) contains 90. 

 The unit of measurement is the degree, or ^ of the circum- 

 ference of a circle. 



Circular, or angular, measure is used principally by surveyors, 

 navigators, astronomers, and by technical men generally, for 

 measuring angles and arcs of circles. 



METRIC SYSTEM OF MEASURES 



The metric system is based on the meter, which, according 

 to the U, S. Coast and Goedetic Survey Report of 1884, is 

 equal to 39.370432 in. The value commonly used is 39.37 in. 

 and is authorized by the U. S. government. 



'There are three principal units the meter, the liter (pro- 

 nounced 'lee-ter'), and the gram, the. units of length, capacity, 

 and weight, respectively. Multiples of these units are obtained 

 by prefixing to the names of the principal units the Greek words 

 deca (10), hecto (100), and kilo (1,000); the submultiples, or 

 divisions, are obtained by prefixing the Latin words deci (f), 

 centi (rio), and mill duVo). These prefixes form the key to the 

 entire system. The abbreviations of the principal units of 

 these submultiples begin with a small letter, while those of the 

 multiples begin with a capital letter. 



