216 THE WEATHER. 



comes is moving much more swiftly. It will of course be 

 left behind. In other words it will appear to move 

 towards the west. This is the explanation of that great 

 aerial current which is constantly-flowing from east to 

 west over all the equatorial regions. 



The Gulf Stream is one remarkable consequence of 

 this wind : and another, quite as striking, is seen in its 

 effects on the nature and length of sea voyages, and the 

 tracks of ships. These winds are so regular that seamen 

 sometimes go much out of their direct course to meet or 

 to avoid them ; and persons not aware of this fact are 

 much surprised in reading accounts of voyages to find 

 the ships, whose adventures they are following, sometimes 

 very far from the track which it might have been sup- 

 posed they would pursue. 



(6) Monsoons. 



In various parts of the earth, within the tropics, there 

 are periodical winds which blow six months in one 

 direction and six months in the opposite. They are 

 called Monsoons. It is unnecessary for our present 

 purpose more particularly to describe them, than to say 

 that they prevail most extensively in various parts of Asia, 

 and especially in the northern part of the Indian Ocean. 

 When they change in the spring and autumn, the winds 

 are for some time variable and violent, and the aspect of 

 the sea and skies very unfavorable to navigation. 



(c) Land and Sea Breezes. 



In warm climates there is on the shore of the sea a 

 breeze blowing towards the land in the night, and towards 

 the sea in the day. The cause is obvious. The land 

 becomes heated by the sun, and the air rises from it, and 

 a fresh supply comes in from the sea to fill the vacancy ; 

 for the sea, not reflecting the sun's rays so strongly, 

 does not heat the air over it so soon. In the night, how- 

 ever, the current is reversed. The land becomes cooler 

 than the sea, and the atmosphere moves from the warmer 

 to the cooler region. The following very happy illustra- 

 tion of this process has been quoted many times in books 

 on this subject It is so clear and complete that it 

 deserves to be perpetuated. 



