98 DEATH AND RESURRECTION. 



of — heat, which is the physical source 

 of energy of all living beings. 



That heat increases the distances be- 

 tween molecules is already evident 

 from the fact that all bodies increase 

 in volume when heated, a process which 

 may be continued by further supply of 

 heat until the solid becomes a fluid, 

 and the fluid a gas. 



In solid bodies the attracting forces 

 have predominance. The molecules are 

 arranged with definite spacing and in 

 definite positions so that the body as- 

 sumes a certain external shape. If 

 such a body is exposed to heat the 

 molecules are removed from each other 

 and the cohesion becomes correspond- 

 ingly feebler. Finally a point is reached 

 when the molecules are so far unfet- 

 tered that they are at liberty to move 

 with respect to each other. The solid 

 has then become a fluid and may 

 through continued heating enter the 

 gaseous state. The cohesion is then 

 entirely conquered so that the mole- 



