10 THE REALITIES OF MODERN SCIENCE 



public and its statesmen of a few of the problems 

 involved. 



With the control over fire, and the consequent ability 

 to cook food and to maintain a comfortable living 

 temperature, man's ascent toward civilization really 

 began. During this time he devised and employed 

 many simple machines, some of which we shall describe 

 in a later chapter. From living in crude shelters of 

 boughs and leaves or in caves he came to live in tents 

 and houses. From being dependent on wild fruits 

 and meats he advanced to agriculture. Animals of 

 burden were used as machines with internal sources 

 of energy. Boats were made and fitted with oars, 

 which are of course simple machines, and also with sails 

 by means of which the energy of the wind could be 

 utilized. Larger groups of men could now exist in 

 the same region, and cities and villages were formed. 

 With the lessening of the struggle for existence man 

 obtained more time for thought and mental develop- 

 ment. The large empires of the ancient world and 

 their civilizations were founded on these elementary 

 advances in the knowledge of the physical world. 

 Language and the arts had developed so that with two 

 of these empires, Babylon and Egypt, history as we 

 know it really began. With these there also began 

 that arrangement and correlation of knowledge which 

 we call science. 



Both the Babylonians and the Egyptians were 

 agricultural peoples, one living in the fertile valley of 

 the Euphrates, the other on the banks of the Nile. 

 What scientific advances they made were mostly along 

 lines of immediate practical value. Thus, the Egyp- 



