140 Mr Lawson on (he Trade-Winds at Barbadoes. 



temperature of the sea in November, December, and January, 

 and the increase of that of the continent of South America, 

 restored the trade in all its former force, and, during these 

 months, the south-easterly winds almost disappeared. 



15. The winds in the West Indies were much affected by the 

 moon's declination and her time of transit. The chief cause 

 of the trade-winds is undoubtedly the higher temperature com- 

 municated by the sun's rays to the atmosphere in the neigh- 

 bourhood of the equator than in the extratropical latitudes ; 

 and, while the difference is sufficiently great, a brisk trade 

 prevails, and the effect of the attraction of the sun and moon 

 is not very obvious ; but when, during summer, the sea and 

 superincumbent atmosphere in the vicinity of the tropics be- 

 come much warmer, and the strength of the trade is much 

 abated, this becomes apparent, and to it all the greater devia- 

 tions of these winds from their regular course seem attributable. 

 I am not aware that the direct dependence of the winds in 

 intertropical latitudes, or the attraction of the sun and moon 

 on the atmosphere, has ever been made out, or, indeed, scarcely 

 hinted at. My attention was first directed to the subject in 

 June 1841, by observing the anomalous directions of the wind 

 during that month, which seemed quite at variance with the 

 usually received opinion as to the cause of the trade-winds. 



IG. The observations of Flaugerques at Viviers, shew a de- 

 cided alteration in the height of the barometer under the dif- 

 ferent phases of the moon, and also under the perigee and 

 apogee. Mr Howard's observations in this country exactly 

 correspond with those of Flaugerques. Some months after 

 my return to England in 1 842, I became aware of the re- 

 searches of Mr Howard and Mr Lubbock on the influence of 

 the moon's declination on the height of the barometer.* I 

 have since seen the notice of the paper of Lieutenant Lefroy, 

 E.A., on the influence of the moon on the height of the baro- 

 meter at St Helena.! In this it is stated, " that the moon's 

 passage over both the infei-ior and superior meridian produces 

 a slight increase of pressure ; a maximum in the curve occur- 



• Lond. Edin. and Dub. Phil. Mag., vol. xviii., pp. 552-5. 

 t Id., vol. xxi., p. 227. 



