I 4 ELEMENTARY SCIENCE 



from one form to another. But, really, water is not active. 

 It is heat that is active. Water is passive, and it is changes 

 in the amount of heat that are responsible for the changes 

 of water. Water is a sort of tool, and heat is the great 

 force that uses that tool. We say that the heat of the 

 sun draws water up. It changes from liquid to gas. Then 

 it changes from gas back to liquid again, and falls as rain. 

 It keeps moving and changing all the time. It goes down 

 deep into the soil and into crevices in the rock, and then 

 again it rises in the air far above the earth. Water is a 

 wonderful traveller. It is in the bodies of plants and 

 animals as well as in the seas and lakes, and it travels 

 from the fields of ice and snow in the far north and south 

 down to the tropics again. Yet with all this movement 

 and changing of form there is always practically the same 

 amount of water in the world. It may change its form and 

 its place, but it is not destroyed. 



So, even by studying water alone we learn that we live 

 in a very changing world. Our surroundings are con- 

 stantly changing, just as we ourselves are constantly 

 changing. 



We do not need to travel to see these changes. We can 

 stay where we are and watch day change into night. We 

 can watch the clouds marching across the sky, and the 

 storms as they gather and break. We can feel the wind 

 and the rain in our faces, and can see the rivers running to 

 the sea. We watch the procession of the seasons, winter 

 changing to spring, and autumn to winter again. Each 

 day the country is a little different from what it was the 

 day before. The plants and the animals change as well as 

 their surroundings. Each week of the spring and summer 

 months you will find different birds and insects in the 



