136 Mr Lawson on the Trade-Winds at Barbadoes. 



towards the end of summer, and that of the sea to the north- 

 ward still more, as shewn by the following observations made 

 by Mr Battersby, 47th Regiment, in the beginning of Septem- 

 ber 1841. A similar series, made by myself in February 1842, 

 is subjoined, which will afford a very good idea of the effect 

 of season on the temperature of the sea in this neighbourhood. 

 The observations have been corrected for the errors of the 

 corresponding instruments. 



In several instances, in this table, the longitude is not given ; 

 but, as the ship's track lay to the eastward of the Caribbean 

 Islands, no material error will arise from the omission. In 

 September, the outer limit of the NE. trade, in 64° W. long., 

 was not well defined ; in February, in long. 60° W., it was 

 about lat. 26° N. 



8. The diurnal variation of the temperature of the air over 

 the sea, within the tropics, is very smcall, and the mean tem- 

 perature is rather under that of the surface of the sea at the 

 place,* a fact borne out by most observations I have met with. 

 It may therefore be concluded, that the air, in passing through 

 the region of the trades, has its temperature increased to the 

 same extent as the sea, while the dew-point is at the same time 

 considerably I'aised. 



9. On my arrival in the West Indies, I commenced to ob- 

 serve the courses of the different strata of clouds, as recom- 

 mended in the Report of the Committee of Physics and Me- 

 teorology of the Royal Society, for the purpose of determining 

 the existence of crossing currents at different heights in the 

 atmosphere. These were at first made with very little regu- 

 larity or method ; but, from the beginning of September, I be- 



* Pouillet, Elemens de Phypiqne.. torn, ii., p. 519, 



