730 Thirteenth Memoir on the Law of Storms in India. [No. 166. 



Now the course and distance made, corrected for 

 variation shewn by the log, is. 



I N. 42. E. 111. 



That shewn by the average wind is, S. 32° W. for ) ^ „ 9 „ 



6.5 hour, or i 



the difference being occasioned by the varying distances made in the 

 different times, arising from the varying strength of the wind, and the 

 effect of the current. The result is always of great interest, for it 

 proves that the vessel, to counteract the current, was obliged to run for 

 one-tenth of the whole time, or ten hours extra in the SWbW. winds 

 (S. 55° W.), and thus though it does not prove that the wind was 

 less strong on the one side (the NW. side) of the storm circle than 

 on the other, it shows that the current must have existed to a great 

 extent. 



The resultant curve made by the average of these different winds for 

 the whole five days is also worth attention, and I have projected it in 

 Fig. III. taking the hours for distances. If this, and Fig. IV. (which are 

 on a larger scale than the other diagrams,) be considered attentively with 

 them, we may, I think, without presumption say that, as they are the 

 only Maps of the winds in such a hurricane yet traced out, so it will, I 

 fear, be long before we obtain such another. 



Its form is also that which theoretically we should say it would assume ; 

 for if we suppose a vortex of air of any size moving through the air (like 

 a dust whirlwind) we should imagine it to be liable to be flattened in on 

 the foremost, and elongated on the following side, and this ours evidently 

 is. If we suppose that the vortex is not one of independent atoms of 

 air moving forward, but of atoms in their usual places to which a rota- 

 tory motion was successively given, like the undulatory movements of 

 particles of water, the same flattening might still occur, though to a 

 smaller degree, and in a different part of the circle. 



A somewhat different curve would be shewn by the number of hours 

 of wind in the five days, with the distance run to each, as shewing 

 the strength of the wind ; the vessel being for the whole time under 

 bare poles.* The resultant of this which is projected at Fig. IV. 

 will be that of the three elements, direction, time, and force, and it will 

 also be the average of all the curves of Fig. I. The table is as follows, 



* And her resistance operating on a large scale like the counter-spring or weight, 

 and friction of an Anemometer. 



