148 Mr Lawson on the Trade-Winds at Barbadoes. 



badoes, to take up the motion. That the process had com- 

 menced was evident from the falling of the barometer ; but, 

 before it was completed, the equatorial current, flowing in the 

 opposite direction, had penetrated the lower stratum of air at 

 a weak point, and, coming in contact with the earth's sur- 

 face, had produced the phenomena already described. 



30. Another instance of the wind being experienced from 

 the SW. at Barbadoes, though still more interesting in con- 

 nection with the present inquiry, occurred on the 6th Octo- 

 ber. The sun''s declination was then about 5° S. ; the moon's 

 hour of transit was ^ 28™ A.M., and her declination on the 

 meridian 26° N. At 9 p.m. on the 5th, the wind was SE. 

 and fresh, and continued from this point at 5 and 9 A.M. of 

 the 6th. About 10|^ A.M. large cumuli and nimbi began to 

 form rapidly to the S. and SW., accompanied by thunder, 

 lightning, and much rain. By mid-day it was quite overcast, 

 and about 1 p.m. the breeze freshened from the SE., with 

 thick rain and thunder ; towards 2 there was a comparative 

 lull for a few minutes, which was immediately followed by a 

 squall from the SW., that continued for about half an hour, 

 with very heavy thunder, and much rain ; towards 3 P.M. the 

 wind fell, the rain ceased, and a slight breeze came on from 

 ENE. At this hour the clouds were chiefly flying from the 

 SE. over the ENE. current, and above the S.E. current 

 there were traces of that from the SW. distinguishable. The 

 same night H. M. ship Hecla experienced heavy weather from 

 the eastward, for five hours, between St Lucia and Barbadoes. 

 31. In this instance the inner margin of the trade was to 

 the northward of the island, a circumstance favoured by the 

 moon passing the meridian early in the morning, with a de- 

 clination of 26° N. As the sun approached the meridian, the 

 temperature he communicated to the atmosphere still farther 

 favoured the ascent of the air from the earth's surface, and its 

 junction with the southerly currents flowing off^ to the north- 

 ward above (19) ; a diminution of pressure thereby occurred, 

 towards which the air flowed from other points with increased 

 velocity. The sun being 10° farther south than on the pre- 

 vious occasion (28), his influence, in reversing the direction of 



