ON THE EARTH'S HISTORY 



times, however, they take a more southerly course, 

 keeping to the south of the British Isles and passing 

 over Central Europe on to Siberia, where they appear 

 to die away. 



Such are the cyclones which are in the main part re- 

 sponsible for British weather ; and the winds that accom- 

 pany them vary a great deal in strength. They depend 

 on the size of the eddy. If the eddy is a very big one 

 (and sometimes the eddies are thousands of miles across) 

 the winds will not be so strong as in the smaller ones. It 

 is, therefore, the smaller ones which cause the violent 

 storms. In the tropical regions whirling eddies of a 

 rather different character occur. To quote Mr. J. H. N. 

 Stephenson : " Instead of being measured by some hun- 

 dreds or even thousands of miles, they are usually only 

 some hundreds of yards across ; and as we found that the 

 smaller the cyclone the more violent the wind, we shall 

 not be surprised that the wind in these is more violent 

 than anything we ever experience in this part of the 

 world. They are called by many different names ; in the 

 West Indies they are known as hurricanes, in the south- 

 east of Asia as typhoons, and in North America as 

 tornadoes. These hurricanes or tornadoes travel much 

 faster than the larger cyclones, and the winds blowing 

 into them are so violent that everything trees, houses, 

 bridges are swept before them, and so strong is the in- 

 draught of air in the centre that strong walls are sucked 

 in just as a piece of paper is in front of a grate when the 

 fire begins to blaze up ; and even heavy metal objects are 

 carried upwards. Fortunately these tornadoes do not 



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