SCIENCE OF COMMON THINGS. 129 



What is heat and heat matter ? 



PART V. 



HEAT. 



CHAPTER L 



NATURE AND ORIGIN OF HEAT. 

 8O7 What is heat f 



In ordinary language the term heat expresses the 

 sensation of warmth which we experience when any 

 portion of our body comes in contact with a substance 

 which is warmer than itself? 



SOS Do we really know what heat is? 



We do not ; we only know and study the effects 

 which it produces on matter. 



SOS To what cause have different philosophers attributed the phenomenon 

 of heat? 



Some have supposed the phenomenon of heat to be 

 merely a species of motion among the minute particles 

 of bodies generally, as sound is motion of another kind 

 among the same particles ; others have supposed that 

 heat arises from the presence of a pecuUa/r fluid or 

 ethereal kind of matter. 



S1O Is it generally believed at the present time that heat is a material 

 substance ? 



It was believed formerly that heat was a kind of 

 matter ; but now it is generally considered that heat 

 has no material existence. 



811 What great fact is opposed to the idea that heat has a separate 

 material existence as a fluid ? 



The fact that nature nowhere presents us, neither has 

 art ever succeeded in showing us, heat alone in a sepa- 

 rate state. 



