Mr Lawson on the Trade-Winds of Barbadoes. 365 



operating on the denser stratum of the atmosphere in the 

 vicinity of the earth, counteracting gravitation, and causing 

 its transfer upwards.* 



41. The other view has been maintained by Professor Dove, 

 of Berlin, Mr Redfield, and Colonel Reid. Accordhig to it, 

 hurricanes and great storms are gyratory, the wind flowing 

 in a circle round a centre, and subsequently pursuing a di- 

 rection, at every point of its course, perpendicular to what it 

 would have followed were the opinions of Epsey or Hare 

 correct. The facts adduced by Dove, Redfield, and Reid, all 

 support the gyratory course of the wind in great storms, and 

 are quite at variance with the views of Epsey and Hare. 



42. Much misconception has been produced on this point, 

 by supposing that the causes of the so-called whirlwinds, and 

 of the hurricane, are the same, though they do not necessarily 

 have any thing in common. The whirlwind is a phenomenon 

 of very limited extent, which chiefly occurs during warm 

 weather, when the air in contact with the earth is still, 

 while the hurricane aff^ects the atmosphere to a considerable 

 extent, and only arises when there are opposite currents which 

 are, obviously, intimately connected with its origin and course. 



43. Mr Redfield, so far as I am aware, has not attempted 

 to explain the origin of hurricanes. Colonel Reid thinks 

 that they may be, in some manner, connected with the mag- 

 netic intensity, as they are frequent in the Caribbean and 

 China Seas, where the magnetic intensity is very great, 

 while at St Helena, where it is remarkably low, they are 

 quite unknown. t This, however, is a mere coincidence, and 

 does not seem in any way connected with the immunity of 

 St Helena from storms, the real cause of which is its position 

 in the midst of a large expanse of ocean, nearly equidistant 

 from the polar and equatorial margins of the SE. trade-wind* 

 and when the different superimposed currents in the atmo- 

 sphere flow quietly onwards, without being liable to those 

 sudden influences, or abrupt alterations of direction, which 

 are so common in the Caribbean Sea, at least, about the 

 inner margin of the trade-wind. 



* London, Edinburgh, and Dublin, Philosophical Magazine, vol. xix. p. 430. 

 t Reid on the Law of Storms, 2d edition, with additions, p. 509-10. 



