TOO Inquiry concerning Ike Nature of Heat, 



ened jsr covered with other substances, the vessel was 

 found to cool much more rapidly. 



A large proportion of the frigorific rays from the sur- 

 rounding colder bodies were, in the former case, reflected 

 at the polished surface of the metallic vessel; but, in 

 the latter case, more of them were absorbed. 



When a large drop of water rolls about without being 

 evaporated upon the flat surface of a piece of red-hot 

 iron, the surface of the drop, is -polished; and, the calo- 

 rific rays being mostly reflected, the water is very little 

 heated, notwithstanding the extreme intensity of the heat 

 of the iron and its nearness to the water. 



If the iron be less hof, the water penetrates the pores 

 of the oxide which covers the metal, the drop ceases to 

 have a polished surface, acquires heat very rapidly, and 

 is soon evaporated. 



If a drop of water be placed on the clean and polished 

 surface of a metal not so easily oxidable as iron, it will 

 retain its spherical form and polished surface under a 

 lower degree of temperature than on iron ; and conse- 

 quently will be less heated, and less rapidly evaporated 

 by a moderate heat. 



If a large drop of water be put carefully into a clean 

 silver spoon, previously heated very hot (that is to say, 

 so hot as to give a loud hissing noise when touched with 

 the wetted finger, but much below the heat of red-hot 

 metal), the drop will support, or rather resist^ this heat 

 for a considerable time ; but after the spoon has been 

 suffered to cool down nearly to the temperature of boil- 

 ing water a drop of water put into it will be evaporated 

 instantaneously. 



It appears, from the results of these experiments, to 

 be probable that under high temperatures air is attracted 



