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LECTURE II. 

 EXPERIMENTAL PHILOSOPHY. 



ATTRACTION. 



BEFORE we proceed to the higher branches of 

 science, it will be necessary to explain what is 

 usually meant by attraction, and the different 

 kinds which have been distinguished by modern 

 philosophers. In the first lecture I called your 

 attention to the effect which follows when you 

 throw a stone, or shoot an arrow upwards into 

 the air. Instead of proceeding according to the 

 direction in which you sent it, you see its force is 

 quickly spent, and it returns to the earth with a 

 velocity increasing as it descends. Now it is easy 

 to conceive that the resistance of the air may 

 stop it in its progress ; But why should it return ? 

 Why should not the resistance of the air stop or 

 impede it in its return ? 



The answer you will think very plain It is 

 its weight that brings it back to the earth, you 

 will say, and it falls because it is a heavy body. 

 But what is weight? Or why is it heavy? It is, 

 in truth, the earth which draws or attracts the 

 stone or the arrow towards it ; this overcomes the 

 force with which you sent it from you at first, 

 and the resistance which the air would otherwise 

 make to its falling. It is the force required to 



