MODES OF DIFFUSING HEAT. 343 



heat of Fusion and of Solution ; Freezing Mix- 

 tures ; Solidification, and the Temperature of 

 Solidification ; Heat from Solidification ; 

 Change of Bulk during solidifying; the Latent 

 Heat of Vaporization ; the Condensation of 

 Gases ; the Latent Heat of Water and of 

 Steam; illustration and definition of Specific Heat; 

 specific heat Determined by Mixture; specific 

 heat Determined by Melting Wax; tables of 

 specific heat, and the Specific Heat of \Vater. 



ECTfON IV, 



MODES OF DIFFUSING HEAT. 



537. Diffusion of Heat. Heat is diffused in three ways: 

 by conduction, convection, and radiation. Whatever the mode of 

 diffusion, there is a tendency to produce uniformity of temperature. 



538. Conduction. If one end of an iron poker be 

 thrust into the 'fire, the other end will soon become too 

 warm to bo handled. It has been heated by conduction, 

 the molecules first heated giving some of their heat to those 

 adjacent, and these passing it on to those beyond. There 

 was a transfer of motion from molecule to molecule. TJie 

 process by which heat thus passes from the hotter 

 to the colder parts of a body is called conduction 

 of heat. The propagation is very gradual, and as rapid 

 through a crooked as through a straight bar. 



539. Differences in Conductivity. If, instead 

 of an iron poker, we use a glass rod or wooden stick, the 

 end of the rod may be melted or the end of the stick 



