Mr Lawson on the Trade-Winds of Barbadoes, 373 



neously occurring in the NW. current, then next above it.* 

 This, having its velocity increased by the same cause which 

 led to the acceleration of the superior strata of the trade- 

 wind, must have been flowing to the SE. with great rapidity 

 over the storm already raging ; but, as the two currents 

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

 bed of air of variable thickness between them (32), which 

 may be subject to gusts in either direction, but which cannot 

 have a determinate motion. 



60. As the NW. current flows over the storm, its plane of 

 motion, instead of being nearly parallel to the earth's surface 

 as previously, will become somewhat inclined to it, dipping to 

 the southward. Being thus directed downwards, it will 

 readily penetrate the still or nearly still air, in the triangular 

 space mentioned above (58) to the eastward of the central 

 margin of the trade wind (C A. Fig. 2), and will be experi- 

 enced as a strong NW. gale, whereon it impinges on the 

 earth's surface. In consequence of the interposed bed of 

 still air between the NE. and NW. currents, after the dis- 

 appearance of the former, at any point of the storm's course, 

 and before the occurrence of the latter, there will be a short 

 period of calm, liable, however, to heavy gusts from either 

 point, or from the intervening ones. 



61, When the NW. current becomes directed downwards, 

 its velocity will be thereby increased ; and the latent support 

 being thus withdrawn from those portions of the current to 

 the NE. and SW. of that first affected, they will have a 

 tendency to flow towards the line of least pressure, as is 

 shewn above would occur in the trade-wind {^^, 57). Thus, 

 to the NE. of the line of least pressure in this current, the 

 direction of the current would become first NNW., and farther 

 to the east it would even come to N., and the velocity ac- 

 quired by those portions of air, being in addition to that they 

 previously had to the SE. in common with the remainder of 

 the cuiTent, they would, in like manner as in the trade-wind, 

 be productive of the most violent effects, and farther tend to 



* It will be shewn further on, that, in certain storms in the West Indies the 

 NW. current is not experienced, and that their characters are thereby very 

 much modified. 



