MATTER AND ITS PROPERTIES 49 



kind of matter. Hardness is a property of rock; magnetism 

 is a property of iron; red color is a property of blood. To 

 name the properties of a substance is to describe it. For 

 example, water is a colorless, transparent liquid. 



There are three properties which are possessed by all 

 matter, living and non-living, 'elements, compounds, and 

 mixtures. These properties are extension, weight, and 

 inertia. 



45. Extension. Every body has extension in three di- 

 rections, i.e., it has length, width, and thickness or depth. 

 Examples: a block, a pencil, a ball. The space which a 

 body occupies is called its volume. A body 8 in. long, 3 in. 

 wide, and 2 in. thick occupies 48 cu. in. of space, or has a 

 volume of 48 cu. in. 



A straight line drawn on a sheet of paper represents exten- 

 sion in one direction only, and a surface marked off on a 

 table-top has extension in two directions only; therefore, the 

 line and the surface are not bodies. 



46. Systems of Measures. The units used in measur- 

 ing extension by the British system of measures (the inch, 

 foot, yard, rod, and mile) have no common relation to each 

 other. An inch is one twelfth of a foot; a foot is one third of 

 a yard; and the relation of the foot or the yard to the rod 

 involves a complex fraction. In the French or metric sys- 

 tem, every unit of length is one tenth of the next higher, or 

 ten times the next lower denomination. 



So much time can be saved in computation by the metric 

 system that the United States government has authorized 

 its use in government work. In most colleges and many 

 manufactories, scientific measurements are made in metric 

 units. It is hoped that in time the metric system will come 

 into general use in the United States, as it has now in most 

 countries of Europe. 



The decimal system of money was adopted in the United 

 States more than a century ago, and some of its denomi- 



