Mr Lawson on the Trade-Winds at Barbadoes. 139 



the air over the land was tlius less. This was still farther re- 

 duced by the occurrence of frequent heavy showers, which 

 never failed to cause a considerable fall of the thermometer, 

 and must have prevented the air, at a very slight elevation, 

 from acquiring that increase of temperature, by the regular 

 interchange of the lower and w'armer strata with those above 

 in passing over the land, which, under ordinary circumstances, 

 would have taken place. The tendency of the air over the 

 land to ascend during the day was thus, in a great measure, 

 done away with ; and it is obvious, by the numbers in the table, 

 that the trade-wind assumed its normal coui'se, and the sea 

 breeze disappeared. 



14. In August, September, and October, which are called the 

 hurricane months, the winds from the southward of E. again be- 

 came prevalent, and they affected the atmosphere to a con- 

 siderable height, being then, for the most part, accompanied 

 by a movement of the lower clouds in the same direction. In- 

 stances undoubtedly presented themselves, in which the direc- 

 tion of the wind differed two or more points from that from 

 which the clouds were moving, but these were not frequent. 

 The mean temperatures at Barbadoes were 80°.63 Fahrenheit, 

 79'.58, and 79°.72; and the mean maxima, 85^63, 8-i°.09, and 

 84".77, respectively. The temperature of the sea at noon in 

 the beginning of September was 81°.7, and a little to the 

 northward 82°.7 ; temperatures considerably exceeding the 

 mean temperature of the atmosphere over the island, whereby 

 the tendency to the occurrence of a sea breeze was much di- 

 minished. The temperature of the sea, too, being higher 

 towards the outer limit of the trade- wind than at its equatorial 

 one, by increasing that of the superincumbent air (8), and 

 rendering it nearly the same over a large expanse of sea, 

 almost neutralized, as it were, the cause of the trade-winds, 

 but left the atmosphere at a higher temperature, and con- 

 taining a large quantity of aqueous vapour, liable to be acted 

 on by any disturbing cause. The gradual diminution of the 



that tlie lowest temperature which occurred during mystaj'in Barbadoes, 

 viz. 69\8 Fahr., was on the afternoon of the 27th June, during an un- 

 usually heavy fall of rain. 



