156 EFFECTS OF HEAT. 



is evaporated, the box is not hot enough ; 

 but if the saliva runs along the box, it is. 



Q. Why is the BOX HOTTER if the saliva 

 RUNS ALONG THE BOX, than if it adheres to it till 

 it is evaporated. 



A. If the saliva runs along the box, 

 the iron is hot enough to convert the 

 bottom of the drop of spittle into vapour ; 

 but if the saliva will not roll, the box is 

 not hot enough to convert the bottom of 

 the drop of spittle into vapour. 



CHAPTER XII. 



4. EVAPORATION. 



Q. What is meant by EVAPORATION ? 



A. The dissipation of liquid by its 

 being converted into vapour. 



Q. What EFFECTS are produced by evaporation ? 



A. The liquid vaporized absorbs heat 

 from the body whence it issues ; and the 

 body deprived of the liquid by evaporation, 

 loses heat thereby. 



