302 



NA TURE 



\yan. 24, 1889 



a mean of those observed during the four years. The 

 diameter of the circle is 600 miles. 



The average force of the wind according to Beaufort's 

 scale (o- 1 2), at various distances from the centre, expressed 

 in nautical miles, is shown in the following table, but 

 owing to the typhoons differing so much in size the figures 

 representing the mean values are often widely different 

 from the values obtained from observations made in a 

 particular typhoon. That is not the case with the direc- 

 tion of the wind, which depends upon the bearing but not 

 upon the distance from the centre or the size of a 

 typhoon. 



Peak. South Cape. China Sea. 



9 ... 9 ... II 

 6 ... 6 ... — 

 5 ... 4 - 6 

 This table proves the wind to be strongest over the open 

 sea, and also, though to a less extent, at some height above 



sea-level. The force of the wind increases at a greater 

 rate on approaching the centre at sea, and that is to a 

 certain extent likewise the case at South Cape, which is 

 far from the mainland and soon reached by typhoons 

 arriving fresh from the Pacific Ocean, where most typhoons 

 originate, although some of them are formed to the west- 

 ward of the Southern Philippines. 



The force of the wind is much greater behind the centre 

 than in the anterior semicircle both at sea and on shore, 

 and the consequence is that the strongest blow is not 

 experienced till the barometer begins to rise. For 

 instance, at an average distance of about 160 miles, the 

 mean force in Hong Kong is 7 to the north, 3 to the west, 

 6 to the south, and 5 to the east. At South Cape (For- 

 mosa) it is 6 to the north, 5 to the west, 7 to the south, 

 and 6 to the east. To the north of a typhoon the wind is 

 remarkably fresh along the southern coast of China, even 

 when the centre is over 300 miles away. It makes an 



A Typhoon in Hong Kcng. 



impression as if the trade-wind was blowing in the 

 middle of summer, while a typhoon moves westward in 

 the China Sea. In So.thern Formosa, where typhoons 

 moving north-westward predominate both in number and 

 in intensity, the wind is strongest to the south or south- 

 east of the centre. 



At Victoria Peak the force of the wind does not depend 

 upon the bearing of the centre, or at any rate only slightly 

 so. It follows that the wind-force registered there just 

 before the approach of a typhoon considerably exceeds 

 that registered at the Observatory. The difference in 

 force is only about one on Beaufort's scale, when the 

 centre is north or west of the colony, and while the centre 

 13 situated to the southward it usually blows harder at 

 sea-level than on top of the Peak. W. Doberck. 



THE STATE OF VESUVIUS. 



THE " Note " in Nature (p. 184) on the state of the 

 Vesuvian volcano has been copied by many news- 

 papers, and I have received a number of letters asking 



To satisfy this desire, I give the 



to what occurred subsequent 



and to the information above 



for further information 

 following particulars a 

 to December 15, 1888 

 mentioned. 



During the remainder of the month of December, the 

 vent was extremely active, ranging from the second to 

 the fourth degree of activity, so that the cone of eruption 

 was often quite red, after a burst, from the large number 

 of lava cakes falling on its sides. This constant ejection 

 of fragments of red-hot pasty lava rapidly increased the 



