Mr Lawson on the Trade- Winds at Barbadoes. 1 41 



ring at both (that of the latter being slightly greater), while the 

 minima correspond to the moon's rising and setting." It is 

 likewise stated, that " the pressure is greater about the period 

 of new moon, and greater in the third and fourth than in the 

 first and second quarters." Lieutenant Lefroy also found the 

 pressures under the perigee to be greater than under the 

 apogee. 



17. These remarks of Lieutenant Lefroy on the moon's in- 

 fluence on the atmosphere at St Helena, are in perfect accord- 

 ance with the phenomena presented by the winds at Barbadoes. 

 These two islands are in nearly the same latitudes in the 

 southern and northern hemispheres, though there is this dif- 

 ference between them, viz., that St Helena is near the centre 

 of the SE. trade, Avhile the equatorial limit of the NE. trade 

 is frequently to the north of Barbadoes in the summer months, 

 a fact of the highest importance in reference to the winds and 

 storms of these latitudes. 



18. Were the sun or moon to move constantly on the 

 equator, its attraction, when near the meridian, would increase 

 the rapidity of the trade-wind, while it retarded that of the 

 returning or equatorial current, and the result would be an 

 accumulation of air, producing a slight rise in the barometer. 

 A similar result would occur on the inferior meridian, and also 

 on the upper when it passed the inferior meridian ; and these, 

 in both cases, would gradually disappear as the sun or moon 

 approached the intermediate positions. If the sun and moon 

 both bo considered to move on the equator, the sum of 

 their effects on the atmosphere would differ, according to their 

 angular distance being greatest at the conjunction and oppo- 

 sition, and least at the quadratures, the maxima and minima 

 running gradually into each other between those points. If, 

 now, the question of declination be introduced, the points to 

 which the sun or moon would tend to accumulate the atmo- 

 sphere would no longer be the equator, but would deviate on 

 either side of it, their latitude being the same in amount, and 

 of the same name as the declination of the body at the upper 

 meridian ; and of the same amount, but opposite in name, to 

 the declination on the lower. In the case of both sun and 

 moon, the sum of their eficcts would still be greatest at the 



