20 



Hon. Ralph Abercromby. Relation between 



be observed approaching at a distance, mountainous cumulus are seen 

 over this central rain. 



But, just as in higher latitudes, the clonds in front are dirtier than 

 those in rear of the trough ; for when, in the latter portion of the 

 typhoon, the fracto-cumulus begins to break, either blue sky or firm 

 fracto-cumulus becomes visible * Thus trough phenomena appear to 

 be only slightly marked in the Philippines, but very much information 

 on this point could not be procured. 



Lastly in the vortex of the typhoon we find the "bull's-eye" or 

 calm clear spot, a few miles in diameter, surrounded on all sides by 

 the fury of the hurricane. Many accounts received agree in saying that 

 light cirri are usually seen over this area, that near land this space 

 is full of birds taking refuge from the terrific surrounding squalls, 

 and that the heat is suffocating. During the passage of the vortex 

 over Manila, on the 20th October, the thermometer rose rapidly, and 

 the relative humidity decreased to an extent hardly known in the 

 driest months. The universal exclamation was " the air burns." In 

 the succeeding typhoon, November 4th and 5th, no snch central heat 

 was observed, but the intensity of the cyclone was much less. 



The instrumental observations at Manila on these two occasions are 

 almost unique ; but there is no doubt that a clear hot central spot is 

 a normal feature of tropical cyclones. The oppressive heat and great 

 dryness would probably point to the existence of a slight down draft 

 in the core of the cyclone. It is extremely difficult to form a definite 

 conception of such a system of circulation, for there is not the 

 slightest doubt that the main mass of air in the centre of a cyclone 

 is rising. The only reasonable suggestion which has yet been made, 

 has been proposed by Yettin and Sprung, who think that under 

 certain conditions a local downward eddy is formed in the centre of 

 an atmospheric whirl. We must, however, consider the question to 

 be as yet unsolved, and there is no point in the mechanism of a 

 cyclone to which more attention should be directed. 



But the most remarkable point is that the blue centre does not 

 always coincide with the barometric vortex. Sometimes the blue is 

 in front, sometimes behind, sometimes to one side of the absolute 

 minimum ; and this has been considered as a proof of the inclination 

 of the axis of the typhoon. This non-coincidence of the blue and of 

 the barometric centre of the vortex has been noticed in every other 

 hurricane country, but at present it is impossible safely to do more 

 than record the fact for further investigation. The supposed non- 

 coincidence of the centre of wind rotation with the barometric 

 minimum has been noticed when discussing Indian cyclones. 



All the characteristics of a typhoon are well exemplified in figs. 9 



* Fracto-cunralus is a name applied at Manila to scud and irregular broken 

 cumulus. 



