180 J. Eliot— The South-West Monsoon Storms [No. 2, 



It continued to accumulate energy until the morning of the 12th, when 

 the action of the land on the atmospheric motion in the eastern and 

 north-eastern portions of the cyclone retarded the advance of the vortex, 

 and began to influence the cyclonic motion considerably. This proceeded 

 at first slowly, but, as the storm moved northwards, the destructive effect 

 of the Burmese and Arakan hills increased, so that the rotatory motion 

 was gradually and completely broken up and disintegrated before the 

 afternoon of the 14th, in the neighbourhood of Akyab. There was thus 

 a period of about 48 hours, from the morning of the 10th to that of 

 the 12th, during which the storm accumulated energy. During the next 

 24 hours, the rotatory motion continued almost undiminished, whilst the 

 motion of translation was largely decreased. During the remaining 36 

 hours of its existence, the vorticose or rotatory motion was gradually 

 diminished. 



The force of the winds at and near the centre (which might perhaps 

 be used to measure the intensity of the storm) depends mainly upon the 

 strength of the atmospheric disturbance producing the cyclonic motion, 

 that is, upon the rate at which aqueous vapour is condensed into rain 

 and upon the character and distribution of the rainfall (i. e., whether it is 

 localized and concentrated over a comparatively small area or diffused) . 

 On the other hand, the extent of area over which the cyclonic dis- 

 turbance extends appears to depend mainly, if not entirely, upon the 

 length of time that has elapsed from its formation, and during which it 

 has advanced over the sea area uninfluenced by the land. Hence it is 

 that the most extensive cyclones have been generated in the centre of the 

 Bay, near the Andamans, and have advanced northwards to the Bengal 

 coast. This is not due to any meteorological peculiarity of the Bay in 

 the neighbourhood of the Andamans, but to the fact that a cyclone 

 generated there, and advancing northwards, takes a longer time to reach 

 the land than if it were formed in any other part of the Bay, and has 

 therefore a longer period during which its energy can increase. 



CHAPTER V. 



Concluding Remarks on the Condensation Theory. 



In the preceding pages, all the observations throwing light on the 

 two largest and most severe storms in the Bay of Bengal during the 

 year 1883 have been given, together with a discussion of their more im- 

 portant features. It remains to explain the chief features of the two 

 storms as physical phenomena, and hence also to suggest the theory of 

 cyclonic generation and motion which appears to be applicable to them, 

 and is consistent with our knowledge of the physics of the atmosphere. 



