THE STORY OF NINETEENTH-CENTURY SCIENCE 



deed, one school of meteorologists, of whom Professor 

 Espy was the leader, has held that without such added 

 increment of energy constantly augmenting the dynamic 

 effects, no storm could long continue in violent action. 

 And it is doubted whether any storm could ever attain, 

 much less continue, the terrific force of that most dread- 

 ed of winds of temperate zones, the tornado a storm 

 which obeys all the laws of cyclones, but dffers from 

 ordinary cyclones in having a vortex core only a few 

 feet or yards in diameter without the aid of those 

 great masses of condensing vapor which always accom- 

 pany 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 surround- 

 ing regions of low pressure. As before, all parts of the 

 current will be deflected towards the right, and the re- 

 sult, clearly, is a whirl opposite in direction to that of 

 the cyclone. But here there is a tendency to dissipa- 

 tion rather than to concentration of energy, hence, con- 

 sidered as a storm-generator, the anti-cyclone is of rela- 

 tive insignificance. 



In particular the professional meteorologist who con- 

 ducts a " weather bureau" as, for example, Sergeant 

 Dunn, 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 de- 

 partments 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 record- 

 ing the attendant meteorological conditions. Their so- 



190 



