Tropical and Extra-tropical Cyclones. 



10 



later on November 4th and oth, the wind falling, as he considered, 

 in front, and doing comparatively little damage. 



Again in the typhoon of August 19th, 1881, the wind blew during 

 eight hours with a rapidity of 44 metres a second, and nevertheless 

 did not damage the roofs, because it did not hit from beneath, but 

 from above. 



These facts are very interesting, as similar observations on the 

 variable destruction for equal velocities have been made by Pidding- 

 ton in Bengal ; and the same has been observed on a much less 

 pronounced scale in Great Britain. The utilisation of the idea in 

 forecasting has, we believe, never been suggested by anyone except 

 Faura ; and his views are worthy of the most attentive consideration 

 from those engaged in forecasting hurricanes. 



Faura thinks that this can all be explained by the supposition that 

 the axis of a typhoon is inclined to the earth's surface, instead of 

 being truly vertical, and that the whole system nutates like a 

 top. 



The author, however, believes that there are insuperable difficulties 

 in the conception of a nutating axis of a cyclone, though he does not 

 propose to discuss the question in this paper. The idea that the 

 variation of destruction for the same velocity was due to a slant in the 

 wind has often been suggested before, and though slanting gusts 

 undoubtedly occur, he is not prepared to pronounce a definite opinion 

 on the question, from the evidence at present available. His object 

 in introducing the subject here, was to point out how the variability of 

 destruction can be used in practical forecasting, even if Faura \s 

 theory cannot be maintained as a whole. 



The weather in and surrounding a typhoon is very characteristic. 

 The whole storm is surrounded by a ring of cirrus. Halo is an 

 almost constant precursor of a cyclone, and is sometimes seen in rear. 

 The author made special enquiry on this point, for herein tropical 

 differ very much from extra- tropical cyclones. In Great Britain we 

 rarely see cirrus of any description in rear of a cyclone, still less 

 the formless ice-dust called cirro-nebula by Ley, which is almost 

 essential to the formation of halo. 



The form of cirrus in this ring, especially in front, is typically that 

 known as " cat's tails " or " cock's plumes " (rahos de gallo) ; and there 

 seems to be a tendency for the lines of cloud to radiate from the 

 vortex. This idea was first suggested by Padre B. Vines of Havana, 

 but requires further investigation, for the author was informed at 

 Hong Kong that they had not observed that allineation there. 



All observers are agreed that here, as elsewhere, cirrus is seen 

 before the barometer begins to fall. 



Inside the cirrus comes a ring of dense black cloud, and then a 

 smaller ring of heavy rain and dense nimbus. When a typhoon can 



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