EVAPORATION. 157 



Q. If you WET your FINGER in your mouth, 

 and hold it up in the air, why does it FEEL COLD ? 



A. The saliva quickly evaporates; 

 and (as it evaporates) absorbs heat from 

 the finger, which makes it feel cold. 



Q. If you BATHE your TEMPLES with ether, 

 why does it allay INFLAMMATION and feverish heat ? 



A. Ether very rapidly evaporates; 

 and (as it evaporates) absorbs heat from 

 the burning head, producing a sensation 

 of cold. 



Q. Why is ETHER better for this purpose than 

 WATER ? 



A. Because it requires less heat to 

 convert it into vapour ; and therefore it 

 evaporates much more quickly. 



(Ether is converted into steam with 104 degs- of heat, 

 but water requires 212 deg s - of heat to convert it into 

 steam.) 



Q. Why does ETHER very greatly RELIEVE a 



SCALD Or BURN ? 



A. Because it evaporates very rapidly ; 

 and (while it is converted into vapour) 

 carries off the heat of the burn. 



Q. Why do we FEEL so COLD ivhen we have 



WET FEET Or CLOTHES ? 



A. As the wet of our shoes or clothes 



p 



