LAWS OF MATTER 447 



as a gas. An example of this may be seen in the evaporation of a 

 liquid (sap) obtained from maple trees which leaves behind maple 

 sugar. If sea-water is heated until the water evaporates, salt is 

 left behind. 



Dissolve about one ounce of alum in a cup of hot water. Hang 

 two or three strings in the solution. As the solution cools, crystals 

 will form on the strings. The molecules of alum as they' collect 

 arrange themselves in such a manner as to produce beautiful crystals. 



Osmosis. Cut out the interior of a beet or carrot and fill the space with a 

 thick syrup or molasses. Close the top with a rubber stopper through which 

 passes a long glass tube. Place the carrot in a bottle of water. 



Water will pass through the walls of the carrot, mingling with 

 the thick liquid. The water will pass into the carrot much faster 

 than the syrup will pass out through the walls. This process of a 

 liquid passing through thin membranes into a thicker liquid is called 

 osmosis. Plants get their food and water through the hair roots by 

 this process. Oxygen gets from the lungs into the blood and fish 

 absorb oxygen from the water by means of osmosis. 



Inertia. Inertia is the great force which keeps all bodies in the 

 universe in motion. 



We have all experienced a certain force which tends to push 

 us forward if we have been standing in a moving street car which 

 comes to a sudden stop. The tendency which forces us to keep 

 on going in the direction in which the car had been moving is 

 called inertia. If we happen to be standing still in the car, and 

 the car suddenly starts, we have a tendency to remain in the same 

 spot where we were standing, which causes us to take a step 

 backward quickly in order to keep our balance. 



This force inertia is, expressed in simple words, a force which 

 tends to keep moving bodies in motion in the direction in which 

 they are traveling, and resting bodies at rest. Whenever an auto- 

 mobile or car stops, it must overcome the tendency to keep on 

 going. Whenever an automobile or car starts, it must overcome the 

 tendency to remain at rest. 



So powerful is this law of inertia and its tendency to make things 

 go in a straight line that railroads must bank the outer rail higher 

 than the inner on curves. 



