2 Hon. Ralph Abercromby. Relation between 



Fig. l. 



Diagram of cloud and rain in a British cyclone. The fall lines are isobars, while 

 the dotted lines define the areas of rain and cloud. The full-line arrows denote 

 the direction of the surface winds, the dotted arrows that of the highest 

 currents. 



The side of the cyclone towards which the isobars are packed may 

 also vary indefinitely, but is usually either in front or rear of the 

 longer diameter. On the whole, the compression of the isobars in a 

 typical cyclone seems to he towards the rear of the longer diameter. 



The recognition of the oval form of cyclones is of the utmost 

 importance in discussions as to the compass bearing of the centre 

 relatively to the direction of the wind in any part of a storm field. 



Another most important point is the fact that a cyclone is not an 

 isolated phenomenon, but an episode in the general circulation of the 

 atmosphere. For instance, most British cyclones are formed on the 

 northern edge of a great anti-cyclone which constantly covers the 

 North Atlantic, while tropical hurricanes are always controlled by 

 their surrounding areas of high pressure. 



Before every cyclone, temperate or tropical, there is always a 

 complicated re- arrangement of pressure surrounding the true storm 

 field ; and many of the errors which occur in the handling of ships in 

 hurricanes arise from a confusion between the premonitory and actual 

 disturbances. For instance, in the normal distribution of pressure 

 over the West Indies, these islands lie on the S.W. edge of the 

 great Atlantic anti-cyclone, and it is manifest that a hurricane cannot 

 develop as an isolated phenomenon without disturbing the distribu- 

 tion of pressure beyond the immediate sphere of cyclone activity. It 



