PROGRESS OF METEOROLOGY IN 1889. 251 



a falling barometer, thongb she may be far away from tlie line of the 

 vortex. Now she would experience the same things if she were in the 

 line of progression; but as there is no means of knowing which is the 

 case, the empirical rule is : lie to till the mercury has fallen O.G inch 

 before beginning to run. (British Association Report, 1888, p. 58G.) 



Theory of cyclones. — From a mathematical study of cyclonic motion 

 M. Ilenri Lasnc finds that the "eye" of tropical cyclones (the small area 

 of calm, and of clear sky, in which the air is relatively warm and dry) 

 is accounted for and explained by theory. A regular cyclonic motion 

 of great intensity like that in tropical hurricanes makes possible a feeble 

 descending motion at the center. In theirregular cyclones of temperate 

 latitudes having large horizontal and small vertical extent no such phe- 

 nomena can be developed ; in these the center is not the locus of great- 

 est energy. {Amuiaire 8oc. Meteor, de France, 37^' aiin6e, p. 12G.) 



Tropical cyclones. — W. Doberck discusses the relation of the wind at 

 Hong Kong to the typhoons occurring in 188G and 1887. Only those 

 within 300 miles of the observatory are considered. No connection is 

 found between the distance from the center and the direction of the 

 wind, but the latter depends on the bearing of the center. The wind 

 has a tendency to blow along the southern coast of China when a ty- 

 phoon is raging in the China Sea, so that the wind in such cases veers 

 only about half as much while the typhoon moves westward as in other 

 cases, and for the same reason the angle between the wind and the ra- 

 dius vector is larger than usual when the center is situated to the south 

 of Hong Kong. A cut is given showing the direction of incurvature on 

 all sides of the storm center when in the vicinity of Hong Kong. [Isla- 

 ture, XXXIX, p. 301.) 



Mr. H. F. Blanford has given the results of his study of the incurva- 

 ture of the winds in tropical cyclones as observed in the Bay of Bengal. 

 In order to derive practical rules for navigators he has measured the 

 angle between the wind direction and the radius vector instead of be- 

 tween the wind direction and the isobar, as is done by Professor Loomis, 

 and has restricted the measurements to wind observations of ships at sea 

 within the influence of the storm, and to good observations on the coast. 

 His results confirm the general fact of a great incurvature obtained by 

 Professor Loomis, but differ somewhat in the amount: 



(1) The mean of one hundred and thirty-two observations between 

 latitudes 15° and 22°, within 500 miles of the storm center, gives the 

 angle 122° between the wind direction and its radius vector. 



(2) The mean of twelve observations between the same latitudes, 

 within 50 miles of the storm center, gives the angle 123°. 



(3) The mean of sixty-eight observations l-etween N. latitudes 8° and 

 15°, within 500 miles of the storm center, gives the angle 129°. 



For the guidance of navigators Mr. Blanford formulates the following 

 rules : 



