214 WINDS. 



regularity, and become of high importance to ship- 

 ping. The sea breeze springs up in the morning 

 some time after sunrise, increases in strength till 

 about two or three o'clock in the afternoon, and then 

 gradually falls off. About the time of sunset a per- 

 fect calm prevails. Soon after the land wind gets 

 up, and blows with gradually increasing strength 

 through the greatest part of the night, and begins 

 to lull towards morning. 



These alternating air currents appear on all 

 coasts within the tropics, even on those of the 

 smallest islands, and they occur every day with 

 perfect regularity, unless they are masked or turned 

 from their true direction by other more powerful 

 winds. The land and sea breezes are, for the most 

 part, felt only at a small distance from the shore. 

 On some far-stretching coasts, however, such as 

 that of Peru, their influence reaches a great dis- 

 tance out to sea. 



In the hottest zone of our earth an uninterrupted 

 current of warm air rises from over land and sea, 

 and must be replaced from below; and thus a 

 movement of colder air sets in from higher lati- 

 tudes on both sides towards the equator. The air, 

 that has mounted up, now flows back in the higher 

 regions of the atmosphere on both sides towards 

 the poles, and falling, as it is gradually cooled in 

 its progress, reaches the earth again in the middle 

 or higher latitudes. This is a circulation of the 



