1839] 



to develop the law of Storms. 



377 



may be reasonably supposed the ship is near the extremity of it."* 

 These views too had likewise been entertained by Mr. W. C. Redfield of 

 New York, from a consideration of the storms occurring in the West In- 

 dies. On lAymg down on a chart the position of ships situated at vari- 

 ous places within the ranges of several of these storms, Col. Reid found, 

 that " the more exactly this ivus done, the nearer appeared to he the ap- 

 proximation to the tracks of a progressive ivhirlwindj^ 



To understand the effect of a progressive whirlwind, it is only neces- 

 sary to inspect the figures 1, 2, and 3, PI. 8. In figure 1, the Island, with 

 reference to the circle to the right, would experience a northerly gale; 

 and, supposing the storm— the whirlwind — to be travelling towards the 

 left, or due west, the northerly gale would continue, until, by its progres- 

 sive motion, the island were situated in the centre of the circle, when a 

 calm might be expected ; after which, the gale would assuredly set in 

 from the directly opposite quarter (from the south) ; until, having arrived 

 at the position occupied by the circle to the left, the storm would here 

 cease. 



If, instead of an island, we consider the case of a ship under sail, the 

 circumstances might be considerably altered ; for, were the ship's course 

 ^he same as that pursued by the storm, it might, by keeping pace with 

 the storm, continue for days within its influence ; whereas, by an oppo- 

 site course, it would in a comparatively short time be got rid of. If the 

 ship were situated at c, as in fig. 2: supposing the direction of the whirl- 

 wind to follow the course abed, then, the wind at the commencement 

 of the gale would set in from the N. E, ; after which it would shift to the 

 east, and terminate eventually at S. E. : but, were the ship situated in 

 the lower portion of the circle (at e), then the wind would set in from 

 the N. W,, after which it would shift to the west, and eventually ter- 

 minate at S. W. If, however, the whirlwind were to follow the direc- 

 tion d c b a ; the direction of the v\^ind, both at the commencement and 

 end of the storm, would be different : for the upper position (c), the wind 

 would in this case commence at S. W.— shift to the west, and terminate 

 atN. W. ; -and for the lower, position in the figure (e), the wind would 

 commence at S. E. — shift to the east, and terminate at N. E. 



Hence it became a matter of some importance, to learn— if whirlwinds 

 In the southern hemisphere revolved in the same direction as did those 

 in the northern. The investigation was difficult, from the few observa- 

 tions which could be met with in the southern hemisphere; but, on the 

 whole, it appeared that there was no exception to the general rule, that 

 the whirlwimls in the northern hemisphere all revolved after the order N. 

 W. S. E. (according to the order of the signs) ; whereas those in the 



* Reid, p. 3. 



