42 A Twenty-second Memoir on the Law of Storms. [No. 1. 



midnight had " heavy gales and hard squalls," so that we may sup- 

 pose the Cyclone circles to have reached her position by this time, 

 that is at midnight 17th to 18th November. 



"We have said above that from the shift of wind experienced by 

 the Coivasjee Family, and that of the Jamsetjee, we might roughly 

 estimate the Cyclone's rate of travelling to be fifty miles in seven 

 and half hours, or, to the nearest decimal, 6.66 miles per hour ; but as 

 the exact positions both of the Jamsetjee and John Adam are uncer- 

 tain, we may also take that of the Erin at midnight on the 18th 

 and 19th, her log being the most carefully kept ; which, supposing 

 the centre to have passed close to her also when she was upset, 

 will give us a distance of 150 miles from the place of the centre ; 

 at 10 p. M. on the 17th to that time, or for an interval of twenty-six 

 hours, or again to the nearest decimal 5.77 per hour, for the Cyclone's 

 rate of travelling. The mean of these two rates 6.66 and 5.77 is 

 6.21 miles per hour. Now as we have a position for the centre 

 at half-past 10 p. m. of the 17th, it follows that if we project 

 the track backwards for these ten and half hours at this rate of 6.21 

 per hour, it will give us about sixty-five miles, and we shall thus 

 obtain an approximate place for the centre at Noon on the 17th. 

 This spot falls in Lat. 12° 10' North ; Long. 94° 8' East and in the 

 absence of better data, I have also marked it with a circle of 150 

 miles in diameter, and this places the position of the JErin at Noon 

 twenty miles without the true limits of the Cyclone circle, and 

 accounts for the squally weather and heavy sea, which she now began 

 to experience. I shall presently advert to the remarkable oscilla- 

 tions of the wind noted in her log. 



To return to the John Adam. It would seem that it was at 4 

 p. m. of the 18th that she was blown over and dismasted, the shift 

 of wind from E. N. E. to South noted in her log, having taken 

 place at 3 p. h., and this we may take to have been the passage of 

 the centre close to her. As before remarked, her position and that 

 of the Jamsetjee are somewhat uncertain, not only from the imper- 

 fect notice of the one and the uncertain drift of the other, but also 

 from the set of the tides and storm currents in the neighbourhood 

 of the Cocos, and the North end of the Great Andaman ; and again 

 the track and rate of travelling of the Cyclone itself, were probably 

 affected by the high land of the North Andaman also. We must thus 



