334 Dove on the Law of Storms. 



At St. Thomas the violence of the tempest was constantly in- 

 creasing up to Ih 30m a. m., when a dead calm succeeded, and at 

 8h 10m a. m. the hurricane recommenced as suddenly as it had 

 intermitted. How can this be reconciled with the meeting of 

 two winds ? Besides, the air at Porto Rico should have been 

 flowing towards St. Thomas at that time, and therefore should 

 have been west, whereas it was N. N. E., just as is required by a 

 whirlwind of which St. Thomas was then the centre. 



A remark of the St. Thomas Observer, Hoskiaer, to the effect, 

 that at each gust the mercury in the barometer sunk two lines 

 and then immediately rose again to the same height as before, 

 shows the diminution of atmospheric pressure to be not the cause, 

 but rather a consequence attendant on the violent movement of 

 the air. 



In considering the progressive advance of the whirlwind, we 

 have not hitherto taken into account the resistance opposed to the 

 motion of the air by the surface of the earth. This resistance, as 

 Redfield justly remarks, causes the rotating cylinder to incline 

 forwards in the direction of its advance, so that at any station the 

 whirlwind begins in the higher regions of the atmosphere before 

 it is felt on the surface of the earth, where therefore the sinking 

 of the barometer indicates its near approach. The inclined posi- 

 tion of the axis causes a continual intermixture of the lower and 

 warmer strata of air with the upper and colder ones, thereby oc- 

 casioning heavy falls of rain, and proportionably violent electric 

 explosions. The cold air appears to precipitate itself from the 

 cloud, and the storm to assume the form called by the Greeks 

 txveyiag. This may also explain the phenomenon known to the 

 navigators of the torrid zone under the name of bulls' eyes, i. e. a 

 small black cloud appearing suddenly in the sky in violent motion, 

 which becoming apparently self-developed, soon covers the face 

 of the heavens, and is followed by an uproar of the elements, 

 rendered doubly striking by the previous untroubled serenity of 

 the sky. 



[M. Dove then quotes from Colonel Reid's work, a very vivid 

 description given by eye-witnesses of the Barbadoes hurricane of 

 the 10th of August, 1831, in which violent electric explosions 

 (both lightning and meteors), the heavy rain, the tremendous 

 force of the wind, its changes of direction, and its interruption by 

 lulls, all form part of the picture.] 



