Jropical and Extra-tropical Cyclones. 



27 



Western Pacific. 



The author has also visited New Caledonia and Fiji to gather infor- 

 mation as to the character of hurricanes in that part of the world. 

 He was not, however, able to collect sufficient materials to justify him 

 in saying more than that those hurricanes seem to differ from those in 

 the Mauritius in little except their smaller intensity. 



The subject of wind in cyclones has already been fully investigated 

 in many countries, but the points on which further research is 

 urgently required are : — 1. The nature of the central " bull's-eye " ; 

 2. The phenomena of the trough ; and 3. The nature of the high 

 pressure areas which immediately surround a cyclone. 



[Note. — The difference of temperature in front and rear of all 

 tropical hurricanes is much less than in extra-tropical depressions. At 

 the outskirts of a hurricane, about the time that cirrus first begins to 

 form in the blue sky, the heat is sometimes very oppressive. The 

 thermometer does not rise much ; but as the ordinary breezes have 

 failed, and been replaced by a suffocating calm, and the increasing 

 humidity diminishes the evaporation of perspiration, the quality of 

 the heat is peculiarly distressing. 



As the sky gets overcast and the rain commences, temperature 

 always falls, and continues relatively low till the sun shines again 

 after the disturbance has passed away. This cold appears to be 

 simply due to the obscuration of the sun's rays by cloud, and possibly 

 partly also to a little cold air being brought down by the heavy rain. 



All this is very different to the temperature disturbance of a 

 British cyclone. The thermometer rises in England rapidly after the 

 sky has become overcast, and remains high until the trough has 

 passed, when a notable diminution of temperature suddenly takes 

 place. 



In a tornado, the rise of temperature in front, and diminution in 

 rear of the disturbance, are very marked, and so far diminish the 

 analogy between a tornado and a hurricane. 



Since this paper was in type the author has had an opportunity of 

 studying Padre B. Vines' > Apuntes relativos a los Huracanes de las 

 Antillas.' That work confirms all the peculiarities of tropical 

 cyclones found in other countries. 



In Cuba hurricanes have the same oval shape and displaced centre 

 as in other tropical countries ; and the same rise of pressure with 

 unusually fine weather occurs just before the advent of the depression. 



The wind is little incurved in front, but very much so in rear ; and 

 a clear "bull's-eye," surrounded first by a ring of squally rain and 

 then by a fringe of feathery cirrus, is the normal distribution of 

 weather round the centre of the hurricane. No trough phenomena 

 appear to have been observed by Padre Vines. — Added June, 1887.] 



