Mr Lawson on (he Trade-Winds at Barbadoes. 149 



the wind as he passed the meridian, was but slightly mani- 

 fested. 



32. It is to be remarked that, when the SE. breeze (30) 

 lulled, the wind did not gradually draw round by S. to SW., 

 but shifted suddenly to the latter point with great violence. 

 Now, when two currents exist in the atmosphere, flowing 

 nearly at right angles to each other, there must always be a 

 certain space between them, in which the direction of the 

 wind is not very decided, or in which the air may nearly be 

 at rest. Should the two currents be directed downwards to 

 the earth's surface, it is clear that the transition from the one 

 to the other would be marked, not by a gradual veering, but 

 by a lulling of the first, and then, after a variable interval, by 

 the more or less abrupt occurrence of the other in the direc- 

 tion in which it was moving. Slight inequalities and eddies 

 may occur in the interposed stratum of air, but, nevertheless, 

 the main features of the case will be as mentioned. 



33. It does not involve an absurdity to suppose that the 

 equatorial current, in these instances, was experienced at a 

 point to the southward of the inner margin of the trade ; for 

 the winds at Barbadoes, up to the 7th September, and on the 

 4th and 5th October, were from the north-eastward, and there 

 would, in consequence, be a returning current at some eleva- 

 tion in the atmosphere, not only then but for some time after- 

 wards. Farther, too, the general tendency of the wind over 

 the northern part of South America, from lat. 4° N. to 10° 

 N., is, according to Humboldt, from the S. from May to Oc- 

 tober ; so that, were the margin of the trade to the north of 

 Barbadoes for several days, the air from the equatorial region 

 would be sufficient to maintain the south-westerly current. 



34. It is advisable to demonstrate, more completely, the 

 influence of the moon on the wind around Barbadoes, by ex- 

 amining, in detail, the observations on its direction and force 

 for a number of days consecutively. For this purpose, the 

 period between the 7th and 21st September, during which she 

 passed from the northern to the southern lunistice, seemed 

 best adapted, as the declination of the sun was then consi- 

 derably less than the latitude of Barbadoes, and consequently 

 the tendency to the formation of a sea breeze (12, 13), whereby 



