LAND AND SEA BREEZES. 213 



wherever neighbouring tracts of land have an 

 unequal temperature, which they impart to the 

 air that hangs over them. In every hot summer's 

 day there are streams of air mounting up from such 

 spots on the soil as are most strongly heated ; these 

 currents carry with them the moisture as well as 

 the warmth of the ground, and they sink again 

 over cooler places, such as surfaces of water and 

 forests. This is well shown by the periodical Land 

 and Sea Breezes, which on many coasts blow from 

 the sea to the land by day, and by night from land 

 to sea. If the land is more heated than the sea 

 during the day, the air that is over the land will 

 mount upwards, and the cool sea air will flow into 

 its place; the air getting cooled in the upper 

 regions falls down again over the sea. During 

 the night, the land is more cooled than the surface 

 of the water ; the latter at last becoming warmer, 

 the air flows from the land to the sea, while the sea 

 air, now becoming lighter, mounts upwards. 



Dove compares this circulation to the turning 

 of a wheel. If the temperature is equal, it stands 

 still ; if it become unequal, it turns, first towards 

 one side then towards the other. Twice daily it 

 stands still, when one of these movements is passing 

 into the other. 



Land and sea breezes occur in high latitudes 

 only during the summer months; in tropical 

 climates, however, they follow with the greatest 



