MECHANICS. 



58. Simple Measurement. 



The first -measurement we are interested in is that 

 of length. We want to know how tall we are, how high 

 a building or a mountain is, and how far it is to a cer- 

 tain place. When you say that you are four feet tall you 

 mean that you are four times as long as the foot meas- 

 ure. You compare your length with this length which is 

 twelve inches. The foot measure is your standard 

 When you measure the length of a building you find how 

 many times the twelve inches are contained in the length 

 of the building. Thus you really divide the length of the 

 thing you are measuring by the length of the standard. 

 Where the comparison of two objects can be expressed 

 as numbers the comparison is always division. 



Our common standards of length are the foot, yard, 

 and mile. Other countries have different standards, and 

 we are gradually coming to use the French system. The 

 chief advantage of the French system is that it is a deci- 

 mal system. Thus 10 millimeters make a centimeter; 

 10 centimeters make a decimeter; and 10 decimeters 

 make a meter. For most science work we use the 

 centimeter. There are no eighths, sixteenths, and other 

 divisions to bother us in our work. We do not have to 

 remember that 3 feet make a yard, and that 5*/2 yards or 

 16J/2 feet make a rod. We are liable to forget the odd 

 numbers and they are hard to multiply and divide. The 



