6 ELEMENTARY SCIENCE 



rain, and working down into the soil as well as running off 

 in streams. Then think of the plants whose roots go 

 down into the soil, and whose leaves are lifted by the 

 stems up into the light and air. From air and earth these 

 plants draw materials that are used in food manufacture. 

 These materials come together in the green leaves, and 

 there, with the aid of the sunlight, the food of the world 

 is made. So we see how sun, rain, and wind, soil and 

 roots, and stems and leaves all help make the world a 

 place where we can live. They are all necessary to our 

 lives. 



Men have greatly improved the plants which they use 

 for food. The trees in the orchards, and the wheat and 

 com in the fields are very different from the wild plants 

 that were their ancestors. Long before the written his- 

 tory of man began, our primitive forefathers were learn- 

 ing through experience how to grow plants for food. Many 

 famines in winter taught them how important it is to har- 

 vest crops and store them. They found that it was a 

 good thing to grow certain plants in places where they 

 scratched the soil with sticks, which was the first kind of 

 ploughing. They learned that the food plants grew better 

 if other plants were kept from growing near them. So 

 they weeded their little cultivated patches. 



So you see that ages ago man began to work as a partner 

 of nature in improving the conditions of life. And we are 

 still engaged in that great work. We have by no means 

 solved the problem. Each year we are finding out new 

 things about nature and about human life. So each year 

 the world becomes a more wonderful and interesting place 

 in which to live. Right now you are living in the most 

 interesting period in the world's history, and to-morrow 



