Mr. W. Brown on the Storms of Tropical Latitudes. 215 



sistance given to its advance towards west, will probably have 

 been sufficient to give a western impulse on its return to por- 

 tions of the earth's surface having a less velocity of revolution. 

 On the eastern side however the air will flow towards it from 

 the eastward of the storm, whilst a portion of the air in the 

 centre will be calm. 



If now we conceive such a mass in motion towards west-north- 

 west as shown by the arrows, at, as is most probable, a very ir- 

 regular rate on account of the occurrence of the calms, it is ob- 

 vious that the veering of the wind will be that observed by Col. 

 Reid ; that at those places over which a part of the storm near 

 the centre passes, the wind will change with the interval of 

 a calm to south-west or south-east, whilst at those on the 

 eastern side it will veer by east, and on the western side by 

 west, the barometer beginning to rise as the wind becomes 

 southerly. The barometer however has been frequently ob- 

 served by W. C. Redfield to rise before the change of the 

 wind, and so decidedly as to make him suppose the axis of the 

 whirlwind to be in an oblique position, the higher part being 

 in advance of the lower, which is retarded by the friction of 

 the earth. This is obviously effected by the check given to 

 the current to the south of the locality at which the rise takes 

 place. 



But these characters of the storm can only continue so long 

 as the course of the upper current remains the same, which 

 we cannot suppose it to do much beyond the tropics, and ac- 

 cordingly some degrees beyond that latitude both the progres- 

 sive motion and the direction of the wind begin to change. 



Now from the data of the two storms before alluded to, 

 which are given only after the gales had passed the tropic, 

 and consequently differ very materially from those given by 

 Col. Reid of hurricanes within the tropics, we find the phe- 

 nomena to be generally as follows : the progressive motion is 

 towards north-north-east, the onset of the wind on the eastern 

 side is most frequently from south-east, but sometimes this 

 direction alternates with north-east, and in both cases the wind 

 changes to north-west. On the western side the storm usually 

 begins from north-east or north-west, but ends, as in the pre- 

 vious instances, from north-west. 



Thus then the direction of the upper current having changed, 

 flowing in its usual course from south to north, the storm 

 no longer maintains the uniformity of its character, but com- 

 mences at the places upon which it arrives during its progress, 

 from three of the eight principal points of the compass, south- 

 east, north-east, and north-west, although it always terminates 

 with the wind from north-west ; thus showing, that although the 



