

254 HEAT ONLY A SENSATION* 



gives out, in the same manner that the oil in a lamp 

 is consumed by the burning of the lamp," are absurd. 

 The light of the lamp does not consume the oil, and 

 as little does the light of a fire consume the fuel. 

 The light is, in these cases, only one of the 

 appearances attendant upon the decomposition of 

 matter, and if it measure any thing it measures only 

 the rapidity with which the decomposition takes 

 place. Further, as light Is reflected from surfaces, 

 and reflected from them though it be invisible pre- 

 vious to the reflection, the light of the sun may be 

 a reflection from the sun, or the sun's atmosphere, 

 which comes invisibly to that luminary from some 

 far distant source. The colours which we observe 

 directly in nature are not visible, and therefore do 

 not exist at any point between the coloured object 

 and the eye; and reflected colours, such as those 

 of the face in a mirror, exist nowhere between the 

 face which is reflected and the eye that sees the 

 reflection. 



So also, in the case of heat, we can never observe 

 it as any thing else than an accompaniment of some 

 action, and intense in proportion to the intensity of 

 that action. From what we can observe and judge 

 of the other appearances attending cold and heat, 

 even heat up to the most intense combustion, all that 

 we can say is, that absolute cold appears to be but 

 another name for absolute rest ; and absolute heat, 

 absolute motion and conflict. 



To speak of " parts" of light and heat, in any 

 sense of the word, is, therefore, to speak that which 

 has no meaning, even if we consider those parts as 

 the mere results of mechanical division. To speak 

 of the half, or the quarter, or any other fraction of 

 light, is absurd ; and one of those absurdities which, 

 having crept into common language, tends to confuse 

 our understanding of things, even in their very 

 simplest elements. 



Air, water, and solid matter we can conceive of 

 as divisible into parts, mechanically, or into pieces 



