HEAT. 37 



and by the intense action of the atoms both heat and light are 

 produced. 



If we put a poker in the fire it becomes red with heat, and, 

 should the fire be made hot enough, it will melt. Why? 

 Because the polarity of the atoms of the iron are reversed, and 

 the mineral atoms of the fire have a greater attraction for the 

 atoms in the poker than the iron has. Gradually, therefore, the 

 polarity of the atoms is reversed, and as the fire becomes hotter, 

 they are repelled from the poker and amalgamate with the 

 atoms in the fire ; for the greater always influences the less. 

 The end of the poker, if held in the hand, is found to be hot 

 also, although it is some distance from the fire. "Why is this ? 

 Because the metal, being conditionally a combustible material, 

 possesses a conductive power of heat, just as it has a conductive 

 power of sound. 



If we hold the hand before a fire we feel it warm. Why ? 

 Because certain atoms in the fire have an affinity to similar 

 atoms in the hand, and are seeking so draw them out. If we 

 can bear it long enough for them to do so (and our hand is 

 burned) then we feel it just as much as if a hook were put into 

 the flesh, and a piece were torn off. 



We now come to the third division, and consider how heat ia 

 produced by friction. 



Supposing we take two pieces of metal, in which, by polarity, 

 the atoms are all lying in one way. That is the "north" 

 pole of one atom, is next in position to the " south " or opposite 

 pole of another, and so on all through, leaving the middle of 

 the atom exposed on the outside of each piece. If we then rub 

 the pieces together, we are disturbing the position of the poles 

 by rubbing similar points together, and as similar poles naturally 



