^6Q Mr Lawson on the Trade-Winds of Barltadoes, 



44, Professor Pove has attributed the gyratory character 

 of hurricanes in the West Indies, to the resistance opposed 

 by the NE. trade to the current from the SW. (about the 

 inner margin of the trade), gradually deflecting the latter 

 from its south-westerly direction to S. and SE.,* which change 

 of motion being continued, would ultimately complete the 

 the circle, ^he general direction of the wind coinciding witli 

 what is actually found to exist. Had Professor Dove been 

 ?iwape of the occurrence of la NW. current in thp atmosphere, 

 >vithin the range of the NE. trade-wind, and of the gradual 

 deflectio^ this undergoes at its inner margin, under the influ- 

 ence of the attraction of the sun and moon, he wowl.d un- 

 doubtedly have materially modified his opinion. 



45. Dr Young long ago ascribed the violence of hurricanes 

 to portions of the upper atmospheric currents prematurely 

 directed downwards, before their relative velocity had been 

 sufficiently reduced by friction on, and gradual mixing with, 

 the lower strata, dashing upon the earth with that tremend- 

 pus force which gives them their distinctive character. Sir 

 John Herschel favours this yiew.f The nearest approach, 

 however, I have met with to the true explanation of the 

 nature and causes of hurricanes, is given by Mr Howard : 

 he says, " The present storm seems to have consisted chiefly 

 in a prodigious aggravation (for the time) of the velocity and 

 force of the currents, which ordinarily proceed to and return 

 from the great equatorial stream. After an obstruction for 

 some considei^able time, of this interchange of air, causing op- 

 pressive heat at the Bahamas, rarefaction suddenly ensues to 

 the SW. of these islands; a portion of the tropical air is rapidly 

 elevated, and the air which supplies its place from the NE., 

 from some cause not as yet apparent, flows in a confined and 

 accelerated stream. That this sti*eam, however, originates in 

 the same cause with the ordinary trade-winds, and is destined 

 to supply the void caused by rarefaction to leeward, is evident ; 

 for it commences with the rising sun, assumes its greatest 

 force at the time the heat of the day is established, and ceases 

 in the evening. Thi^ part of the hurricane flows with steady 



''" Scientific Memoirs, Vol. iii. p. 209-10. 

 t Trfi&tisc on Astronomy, p. 132, Note. 



