82 Materials and Their Handling 



begin to narrow and define themselves along cer- 

 tain lines. 



We Learn by Comparing Observations with 

 the Things Remembered. In our observation of 

 things and our memory of them, we compare our 

 observation with our memory of previous observa- 

 tions and we find that certain things are always 

 associated with certain uses or with certain neces- 

 sities of our lives. We discover that things occur 

 always in the same way when the conditions are 

 the same. If we try to imagine the man who first 

 observed the metallic residue that was left from 

 the brown earth that was next to his hot fire, we 

 can see how the hardness and the brightness of 

 that residue would attract him and how he would 

 try to build just as hot a fire again and put some 

 brown earth in it to see what he could get. After 

 a while he would find that, with a certain sized fire 

 and a given amount of the brown earth, he could 

 always get the same quantity of this hard metallic 

 substance, which we now call iron; and he would 

 gradually learn by these associations how to pro- 

 duce the iron which he had accidentally discovered. 



This process of association of ideas took not 

 one man, but many generations of men to accom- 

 plish. The first man had to bring together in his 

 mind, from a number of observations, the associa- 

 tions or surroundings. The man who learned 

 from him made his first observation with some 

 of the associations already determined up to that 

 point, and from that point he was able to carry 

 liis observations and associations still further. 



