250 PROGRESS OF METEOROLOGY IN 1889. 



Hyrtsometry, — Dr. J. M. Peruter gives the following hypsometric 

 formula : 



t' 4- 1" 

 h == 18399.8 (1 + a ^ ) x 



[1 + 0.378 . jQt+|!5)]x 



(1 + 0.00259 cos 2 q)) X 



f^ 5 2 ^ + /A , fh'\ 



ill wliicli s is the altitude above sea-level of the lower station, and &', 

 h" are barometer heights corrected, not only for temperature and in- 

 strumental error, but for differences in gravity between the two places. 

 Accompanying the formula there is given a series of tables which for 

 the most part have been newly computed. {Rejjertorlum der Physih, 

 1888, p. 161.) 



IX.-CYCLONES; TORNADOES; THUNDER-STORMS; WATER-SPOUTS; GEN- 

 ERAL WEATHER RELATIONS. 



Hurricane tJwories. — Hon. Ralph Abercromby compares the old and 

 the modern views of hurricanes. The old conception was of a circular- 

 shaped eddy, round which the wind blew in circles. Modern research 

 shows that a hurricane is an oval eddy, and that the wind blows in an 

 incurving spiral round the vortex, not round the center of the oval, 

 and that the incurvature is less in front than in rear of the vortex. A 

 hurricane is always changing its shape, so that the vortex is one day 

 on one side of the oval, and towards another side on the next. 



No rule is possible for determining absolutely the bearing of the vor- 

 tex by observations on board a single ship, whereas it used to be stated 

 that facing the wind the vortex bore eight points to the right in the 

 northern and to the left in the southern hemisphere. 



We can say now only, that when fairly within the storm field and 

 facing the wind, the vortex will be from eight to twelve points to the 

 right of the wind in the northern hemisphere and to the left in the 

 southern hemisphere. Greater precision can be obtained in certain 

 circumstances. For example, if a ship is nearly in front of the vortex, 

 the bearing of the vortex will probably not be much more than eight 

 points to the right or left, and in the rear of a hurricane the vortex 

 may bear twelve points to the right or left of the wind., because the 

 wind is there very much incurved. A ship should then always lie to 

 till the barometer begins to rise, otherwise she will be liable to run right 

 into the vortex. 



Modern research has proved that a hurricane is usually imbedded in 

 some prevailing trade or monsoon, and that there is a belt of intensi- 

 fied trade-wind outside the true storm field. This belt is always on the 

 side of the hurricane farthest from the equator. A ship in this belt 

 experiences an increasing trade without change of dipection, and with 



