DIVISIBILITY. 21 



one-half, one-tenth, or one-hundredth of one cubic foot, if the press- 

 ure be increased to 20, 100, or 1000 pounds respectively. On the 

 contrary, the gas will expand to 2, 10, or 100 cubic feet, if the 

 pressure is reduced to 5, 1, or one-tenth pound respectively. Vapors, 

 produced by evaporation of liquids or solids, have the same properties 

 as gases. 



2. DIVISIBILITY. 



Mechanical comminution. All matter admits of being sub- 

 divided into smaller particles, and this property is called divisibility. 

 The processes by which we accomplish the comminution of a solid 

 substance may be of a mechljlrical nature, such as cutting, crushing, 

 grinding, but beside these modes of subdivision we have other agents 

 or causes by which matter may be divided into smaller particles, and 

 one of these agents is heat. 



Action of heat on matter. Let us take a piece of ice and 

 convert it, by means of mortar and pestle, into a very fine powder. 

 When the smallest particle of this finely powdered ice is placed 

 under the microscope and heat applied, we shall observe that it 

 becomes liquid, thus proving that it was capable of further sub- 

 division, that it consisted of smaller particles, which have now by 

 the action of heat become movable. By further applying heat to the 

 liquid particle of water we may convert it into a gas or vapor, which 

 will escape into the air, or which we may collect in an empty flask. 

 The flask will be filled completely by this water-gas (or steam) 

 obtained by vaporizing that minute particle of ice-dust. This fact 

 demonstrates that mechanical comminution does not carry us beyond 

 a certain degree of subdivision of matter. That is to say, the smallest 

 fragment of the finest powder still consists of a very large number of 

 much smaller particles. To the smallest particles which compose 

 matter the name molecules has been given. 



QUESTIONS. 1. What is matter and what is force? 2. Mention the prin- 

 cipal fundamental properties of matter. 3. Mention the three states of aggre- 

 gation. 4. Describe the characteristic properties of matter in the solid, liquid, 

 and gaseous states. 5. What is cohesion? 6. Give a definition of a crystal- 

 lized substance. 7. Under what circumstances will matter crystallize? 8. 

 State the difference between amorphous, polymorphous, and isomorphous 

 substances. 9. What is meant by elasticity or tension of gases? 10. State 

 the law of Mariotte. 



