THE PROPERTIES OF MATTER. 13 



the body is said to fall to the earth. But in this case we have no 

 means of measuring the force that draws the two bodies together. 

 If now the body be supported, the force acts as before and produces 

 pressure upon the supporting substance. This pressure measures 

 the attractive force acting between the earth and the body, and is 

 called weight. If a second body like the first be placed beside it, 

 the mass attraction of the earth is exerted upon twice as many 

 molecules, and, reciprocally, the attraction of twice as many mole- 

 cules is exerted upon the earth; i. e., the attraction has become twice 

 as great, and the measure of that attraction, or the weight, has been 

 doubled. 



(b.) If the same body were upon the moon, its weight would be 

 the measure of the attraction existing between the body and the 

 moon. But as the mass of the moon is less than that of the earth, 

 the attraction between the body and the moon would be less than 

 that between that body and the earth, and the weight would be 

 proportionally diminished. 



34. English Measures of Weight. For the 



comparison of weights, as well as of extension, standards 

 are necessary. In England and the United States the 

 pound is taken as the unit. Unfortunately, we have 

 pounds Troy, Avoirdupois, and Apothecaries', the use vary- 

 ing with the nature of the transaction. As with the yard, 

 these units are arbitrary, determined by certain carefully 

 preserved standards. 



35. Metric Measures of Weight. Ratio 

 = 10. 



f Milligram (mg.) = 0.0154 grains avoirdupois. 



DIVISIONS. J Centigram (eg.) = 0.1543 " " 



[Decigram (dg.) = 1.5432 " 



UNITS. Gram (g) = 15.432 



Dekagram (Dg.) = 0.3527 oz. ' 



Hektogram (Hg.) = 3.5274 " " 



Kilogram (Kg.) = 2.2046 Ibs. 



Myriagram (Mg) = 22.046 " " 



