A HISTORY OF SCIENCE 



zones, the tornado a storm which obeys all the laws 

 of cyclones, but differs from ordinary cyclones in hav- 

 ing a vortex core only a few feet or yards in diameter 

 without the aid of those great masses of condensing 

 vapor which always accompany it in the form of storm- 

 clouds. 



The anti-cyclone simply reverses the conditions of 

 the cyclone. Its centre is an area of high pressure, 

 and the air rushes out from it in all directions towards 

 surrounding regions of low pressure. As before, all 

 parts of the current will be deflected towards the right, 

 and the result, clearly, is a whirl opposite in direction 

 to that of the cyclone. But here there is a tendency 

 to dissipation rather than to concentration of energy, 

 hence, considered as a storm - generator, the anti- 

 cyclone is of relative insignificance. 



In particular the professional meteorologist who 

 conducts a "weather bureau" as, for example, the 

 chief of the United States signal-service station in 

 New York is so preoccupied with the observation of 

 this phenomenon that cyclone-hunting might be said 

 to be his chief pursuit. It is for this purpose, in the 

 main, that government weather bureaus or signal- 

 service departments have been established all over the 

 world. Their chief work is to follow up cyclones, with 

 the aid of telegraphic reports, mapping their course 

 and recording the attendant meteorological conditions. 

 Their so-called predictions or forecasts are essentially 

 predications, gaining locally the effect of predictions 

 because the telegraph outstrips the wind. 



At only one place on the globe has it been possible 

 as yet for the meteorologist to make long-time fore- 



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