176 J. Eliot— ne Suuth-West Monsoon Storms [No. 2, 



near the northern limit of the retreating south-west monsoon current, 

 which is at that period diminishing in strength. It is probably much 

 shallower at its northern limits than elsewhere. Many of the pheno- 

 mena of the cyclones of the Bay appear to be intelligible and explicable 

 only on this supposition. 



If it be granted that the October and November storms of the Bay 

 of Bengal are formed near the northern edge of a diminishing and 

 retreating current, it is hence almost certain that the vapour condensa- 

 tion, in the case of the November cyclone under discussion, occurred at 

 a comparatively small height in the atmosphere, and that the resulting 

 motion was mainly confined to the lower strata. Hence the effects due 

 to friction with land, and to the destructive or disintegrating action of the 

 hill barriers of Burmah and Arakan cutting almost radially across the 

 cyclonic area, would be large and marked. This was undoubtedly the case. 

 So long as the cyclone was to the south of the Burmah coast, the cyclone 

 increased in intensity. When the centre was in a line with the coast, 

 and at a short distance from it, retardation was at once shown, and the 

 cyclonic or vorticose motion began to diminish. And as the centre 

 advanced northwards, so that the Arakan hills (of greater height than 

 the west Burmese hills) were included within the area of disturbance, 

 the disintegrating action became rapidly more marked, and caused a 

 speedy disruption of the vortex. 



A feature which deserves special notice in the smaller cyclonic 

 storms of the Bay is the behaviour of the barometer. The barometer 

 affords practically no indication of the approach of a small cyclonic 

 storm in the Bay, and should not be trusted by the mariner to give due 

 warning. The reason of this is simple. A favourable condition ante- 

 cedent to the formation of a storm is approximate uniformity of pressure 

 over the whole or a large portion of the Bay. If a small atmospheric 

 whirl be set up in an almost quiescent mass of air, which is therefore 

 under nearly identical and uniform conditions, it produces a small de- 

 pression at and near the centre, which extends slowly outwards. The 

 fall of the barometer at distances of 80 or 100 miles from the centre 

 is generally small in amount, and is frequently less than the changes due 

 to general actions common to the whole of India. The depression at 

 the centre rarely exceeds half an inch, and steep baric gradients are 

 confined to its immediate neighbourhood. Over the rest of the Bay, 

 the pressure is slightly affected by the indraught, but frequently not 

 to such an extent as to obscure the changes going on over the whole 

 of India. In other words, during the formation and existence of a 

 small storm, the barometer immediately outside of the storm area prO' 

 per oscillates in obedience to the larger atmospheric movements com- 



