Chap. XL.] 



STANDARDS OF LENGTH. 



487 



a gramme 



being the mass of a cubic 

 centimetre of distilled water at 4 C. 

 A cubic millimetre is a milligramme. 



One gramme (1 g.) = 10 decigram- 

 mes (10 dcg.), - 100 centigrammes 

 (100 eg.) = 1,000 milligrammes (1,000 

 mg.). 



One pound avoirdupois = -453593 kgme. 

 ounce ,, = 28-3496 grammes. 



,, drachm ,, = 1*771 ,, 



grain = 0-064799 gramme. 



In Troy weight : 



One ounce = 31-103 grammes 

 ,, drachm ^= 3 - 881 ,, 

 grain = 0-065 gramme. 



One kilogramme = 15432-349 grains (2-204 



pounds avoir.) 

 gramme = 15-43249 



By the metric system capacity is 

 also measured. Thus, the measure of 

 capacity is the litre, equal to 1,000 cubic 

 centimetres (1,000 cc.). It equals 

 1-76172 imperial joints. 



Force is defined as " whatever 

 changes or tends to change the motion of 

 a body by altering either its direction 

 or its magnitude." If a force act 

 upon a body at rest, it will cause it to 

 move in a particular direction with a 

 particular velocity. If two equal forces 

 act upon two bodies for the same time, 

 and impart to them equal velocities, 

 then the two bodies are of equal mass. 

 So that the velocity of a body is depen- 

 dent not only upon the force which acted 



< u 



Fig. 198. A. 

 Decimetre di- 

 vided into Cen- 

 timetres and 

 MilKin etres. 

 B. Inches and 

 Tenths of an 

 Inch. 



