222 RADIATION. 



Q. Why does not the MIST become DEW ? 



A. Because the chill of the air is so 

 rapid, that vapour is condensed faster 

 than it can be deposited ; and (covering 

 the earth in a mist) prevents any further 

 radiation of heat from the earth. 



Q. When the earth can no longer RADIATE 

 heat upwards, does it continue to CONDENSE the 

 vapour of the air ? 



A. No \ the air (in contact with the 

 earth) becomes about equal in temperature 

 with the surface of the earth itself; for 

 which reason, the mist is not condensed 

 into dew, but remains floating above the 

 earth as a thick cloud. 



Q,. Why does this MIST seem to RISE HIGHER 

 and HIGHER, and yet remain quite as dense below 

 as before? 



A. The air resting on the earth is 

 first chilled, and chills the air resting on 

 it ; the air which touches this new layer 

 ofmistbeing also condensed, layer is added 

 to layer ; and the mist seems to be rising, 

 when (in fact) it is only deepening. 



Q. Why does MIST and DEW VANISH as the 



SUN rises ? 



A. Because the condensed vapour is 



