Mr Lawson on the Trade-Winds at Barbadoes. 133 



Chinese seas, while they have disclosed many highly important 

 phenomena, have, nevertheless, failed to alFord an account of 

 the peculiar circumstances which concur to produce them. 

 These storms in the AVest Indies, at least, commence about 

 the equatorial margin of the trade-winds ; a fact which gives 

 a peculiar interest to the investigation of the atmospheric 

 currents found to exist there. Having been stationed for 

 nearly a year in Barbadoes, an island that has suffered more, 

 perhaps, than any other in the West Indies, from hurricanes, 

 and which was admirably situated for the purpose, I paid a 

 good deal of attention to this subject, and have elicited some 

 facts, which, so far as I am aware, have not hitherto been 

 noticed. 



2. The trade-winds are usually ascribed to the greater 

 heating power of the sun's rays in the immediate vicinity of 

 the equator than elsewhere, expanding the air in contact with 

 the earth's surface, and, by 'thus rendering it specifically 

 lighter, causing it to ascend, while colder air flows in from 

 either side to supply its place; but, as these currents pass to 

 points of the surface where its velocity of rotation is greater 

 than at those which they originally left, and as the aii* com- 

 posing them is some time in acquiring this increased velocity, 

 they assume an easterly direction, instead of coming from the 

 true north and soutlv, as they would have done had the earth 

 been at rest. The ascent of the air at the equatorial limit of 

 the trade is greatly facilitated, especially during the colder 

 months, in the corresponding hemisphere, by the great ad- 

 dition to its aqueous vapour acquired during its passage. 



3. The trade- winds are materially influenced in the vicinity 

 of the West India islands by the configuration of the neigh- 

 bouring coast of South America. This extends from the 

 island of Trinidad, in latitude 10^ X., and longitude 60° W., — 

 on the one h.ar.d, in a sonlh-castcrly direction, for about GOO 

 ItMuucs, and on th(; other, from the same point nearly west. 

 From November to March, the sun being in the southern 

 hemisphere, the South American continent becomes consider- 

 ably warmer than the neighbouring sea, and the NE. trado 

 is felt strongly over the northern half of the former division of 

 the coast, and over the whole of the latter; but, as the sun ac- 



