122 nature^ iflMracles, 



of heat radiation from the earth's surface it 

 is a very easy matter to protect tender vegeta- 

 tion from even quite a severe frost, if it occurs 

 in the early fall, by a slight covering, such as 

 thin paper. The paper will act as a heat 

 screen and in a measure prevent the heat from 

 radiating from the earth immediately under 

 it. Frost which of course is but frozen dew 

 at this season of the year will form on a still 

 autumn night, although the atmosphere at 

 some distance above the ground is some de- 

 grees above the freezing point. The reason 

 for this will be obvious when we consider the 

 facts that have been set forth concerning the 

 power of radiation to produce cold. 



It has been estimated by meteorologists that 

 the amount of water condensed upon the sur- 

 face of the earth in the form of dew amounts 

 to as much as five inches, or about one-seventh 

 of the whole amount of moisture that is evap- 

 orated into the air. It will thus be seen that 

 dew performs an important part in supporting 

 vegetation. 



The same operation in nature's great work- 

 shop that forms the dews of summer creates 

 the frosts of winter. The moisture in cold 

 weather is condensed the same as in warm. 

 When it is condensed at the surface of the 

 earth we have the phenomenon of frost, but 

 when condensed in the upper regions of the 

 atmosphere we have that of snow. 



