SIMPLE MACHINES 175 



and cutting tool, he made a machine with which he could 

 dig up the soil and make it more favorable for the growth 

 of plants. This was primitive agriculture. He also 

 learned to befriend certain animals and to protect them 

 with his weapons. Thus began primitive stock-raising 

 and the use of animals as beasts of burden. 



Then came a comparatively rapid development of 

 machines for clearing the trees and stones from the 

 fields, for transporting some of the trees and stones for 

 building purposes, for erecting larger buildings, and in 

 comparatively recent times for manufacturing and ex- 

 tensive transportation. But we must not lose sight of 

 the fact that the simple devices and tools used by primi- 

 tive man are still used by the most highly civilized people, 

 but with modifications, improvements, and almost an 

 infinite number of additional machines of all kinds. 

 The people of today have the enormous heritage of all the 

 mechanical devices ever thought of by man from primitive 

 times to modern. 



If the leading races of mankind had depended only 

 upon their physical strength to subdue and conquer 

 nature, instead of seeking to invent new devices and 

 to discover new methods of obtaining food and shelter, 

 the world today would be in the condition that is preva- 

 lent in the wild parts of Asia, Africa, and South America, 

 where the natives still use only the crudest tools and 

 implements of primitive man. 



We sometimes wonder how people a few hundred 

 years ago could live at all, when we think of the enormous 

 amount of complex machinery in use today, transport- 

 ing man from place to place and bringing him food and 

 clothing from the most distant parts of the earth. The 

 steamboat, railroad, telegraph, sewing machine, harvest- 



