THE WEATHER. 225 



each particular point through the whole distance will 

 blow in the contrary direction, i. e. from the northeast. 

 This accords with well known facts. 



These principles in regard to the condensation of the 

 vapors ' of the atmosphere, will explain a vast variety of 

 facts. 



A family sit during a winter's evening by their fireside, 

 and their breath fills the air of the room with moisture. 

 In the night the windows become intensely cold, and the 

 water thus diffused becomes condensed upon the glass in 

 beautiful icy crystals, called, usually, frost upon the 

 windows. 



In a summer's day the sun, by warming the atmosphere, 

 brings up into it a large supply of vapor. In the eve- 

 ning the grass and the buildings become cool, and the 

 moisture, previously diffused, becomes condensed in drops 

 of dew, which load the herbage to a degree proportioned 

 to the warmth of the preceding day, and to the coolness 

 of the night. 



A portion of air having been lying upon the surface of 

 the earth, until it is almost saturated with moisture, at 

 length rises. It expands as it ascends, can no longer 

 retain its vapor in an invisible form, and floats, alight 

 fleecy cloud, through the sky. 



In a similar case the condensation proceeds farther. 

 Instead of merely forming those minute globules which 

 are too light to fall and too small to be separately visible, 

 the water gathers into visible drops, which form in the air 

 a black and heavy mass, or descend in showers of rain. 

 If they fall through a very cold stratum in their descent, 

 they freeze into balls of ice : or if the stratum of air in 

 which the condensation takes place is very cold, the vapor 

 shoots into icy crystals, which descend as snow. 



In an afternoon in August a river loads the air above it 

 with moisture. The chill of the night cools the whole 

 mass, and in the morning we find lying upon the stream 

 a bank of fog, which the sun's rays cause to vanish, but 

 which they do not remove. The warmth of the sun enables 

 the air to hold in transparent solution the water which was 

 visible before 



'Beyond Cape Town,' says Arnott, 'as viewed from 



VOL. i. NO. ix. 20* 



