126 Mr. W. R. Birt on Atmospheric fVaves . 



watch. Although this movement partakes of a cyclonic character, 

 in order to distinguish it from that of a true cyclone, which cir- 

 culates around a region of depression, it has been termed anti- 

 cyclonic, as circulating in a reverse direction around a region of 

 elevated pressure. 



Fig. 1. 



STrto>;G vrixD j pos^'EEiob, trough. 





a 







a' 







■-r 



S.W. 



BAROMETER 



POSTERIOR 



S. W. 



p 



s 



^ 



'P 



S. £. 



PALLING. 



SLOPE. 



S. E. 





a 







a 







b' 







1/ 





W 

 y, 



N. E. 



baro:meter 



ANTERIOR 



K E. 



n 



iz; 



> 



b 



RISLN-G. 



SLOPE. 



N.W. 

 b 



STRONG WIND. 



ANTERIOR TROUGH. 



\ 



Fig. 2. 



a. 



SE 



a) 



^ — > 



sw 



SE 



y 



On the 19th of Apri], 1872, the weather-charts show a stream 

 of air along the eastern coast of Great Britain, direction N.N.W., 

 curving over the eastern counties of England and crossing the 

 channel as a N.E. wind. The isobars or lines of equal pressure 

 show the highest barometers in Ireland, and the low^est in the 

 south of France. The gradations of pressure can be arranged in 

 a Table in accordance w^ith the following enunciation. 



