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tions of the atmosphere rise ; colder portions flow in to take their 

 place. Atmospheric disturbances of this kind are constantly 

 occurring everywhere ; but they are of a more marked character 

 in tropical regions, where the storms too are on a larger scale and 

 more violent in their effects. It may be added that, irrespective 

 of latitude, there are everywhere also local influences at work to 

 complicate the movements of the air set in action in this way. 

 From these causes combined, along with others that might be 

 mentioned, the problems in meteorology are rendered extremely 

 intricate, and it must be A'ery long before we can expect thoroughlj' 

 to understand the subject. 



Most of the storms which visit these islands come to us across 

 the Atlantic from America, though after their first rise they ai'c 

 liable to have their direction as well as form much altered from 

 various circumstances as they travel onwards. They are almost 

 all cyclones or partial cyclones, this name being given to them 

 from the disturbed portion of the atmosphere revolving round a 

 centre, where there is an area of more or less deep depression 

 and where there is a calm. " The depression however is of small 

 vertical depth compared with the superficial area over which the 

 storm reaches. Sometimes while the branches of trees and the 

 fragments of the wreck of buildings are being carried by the 

 wind for miles, the clouds above do not indicate the slightest 

 signs of disturbance. The superficial area, on the other hand, 

 which the storm .spreads over is " seldom less than 600 miles in 

 diameter," and occasionally " two or three times that amount." 



The rate at which these storms revolve is very great though 

 variable. " In Europe it frequently amounts to sixty or seventy 

 miles an hour continuously for some time." In the " Eoyal 

 Charter " gale in 1859, above alluded to. Admiral Fitzroy states 

 that the velocity of the wind in spiral eddyings was "from sixty 

 to 100 miles, at a distance twenty to fifty miles from the central 

 depression, where there was a comparatively quiet space.* In the 



* " Weather Book," p. 300. 



