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



deration, and here I think we may fairly reject the latitudes, and conse- 

 quently the longitudes, given on the 25th and 26th, for it is difficult to sup- 

 pose between the " frightful sea," (a literal translation) the motion of the 

 vessel, the mere glimpses of the sun obtained in such weather, and often, 

 if any horizon is seen, the difficulty of knowing if it be the true one, 

 that any correct observation could be obtained. For the same reasons 

 also, the hurricane still continuing, I should attach so little faith to the 

 observation of the 26th, that I have preferred rejecting them both, and 

 taking the two positions of Noon on the 22nd and Noon 27th as fixed 

 and well ascertained points, by which to estimate the average current 

 experienced for the whole five days ; and I think every seaman will 

 agree with me, that this is the safest course as to probability, and con- 

 sequent approximation to the truth. 



2. The nature and strength of the current she experienced. 

 When the Charles Heddle's log is worked for the whole five days 

 with simply the allowance for variation,* she will be found to have made 

 good, as noted on the Diagram Fig. I, a course of North 42' E. distance 

 111', in the five days from November 22nd to November 27th; but 

 by her Chronometer and observations she had really made good, as 

 in Diagram Fig. II. a course of South 55° W. 366'. So that she must 

 during the five days have experienced a current of S. 52° W. 476 miles ! 

 or in round numbers, (which would require 480 miles,) four miles per 

 hour for the 1 20 hours, or five days, of the hurricane. I have already ex- 

 plained why I should reject wholly the observations on the intermedi- 

 ate days, and this compels us to take the whole as a general average, 

 being without any positive knowledge as to whether its force or direc- 

 tion was different on different days. It is clear that if the direction was 



* There is considerable uncertainty as to the variation in this tract between Bour- 

 bon, the Mauritius and the coast of Madagascar. On this last coast it is marked in No- 

 rie's Tables, ed. of 1844, which 1 take to be from the latest authorities, as 16° Westerly 

 at Foul Point, latitude 17| S.; and as 21° Westerly at Fort Dauphin, in latitude 25° S.j 

 and at Mauritius as 14° 20' West, but we do not know how late this is, and if the varia- 

 tion is increasing or diminishing; and I have not access to any very late works or charts. 

 I have thus allowed 1| points for the first three days, and 1| points for the last two. 

 This may be slightly erroneous, but we do not know any thing as to what may have 

 been errors of steerage, misplacing of compasses, and local variation, and \ of a point 

 more or less for a day or two would not make any difference in this kind of circle sail- 

 ing, as I have satisfied myself by working over the logs of 23d and 24lh with J \ point 

 variation, when the result for the two days was only three miles South and four East of 

 that given by the variation used, which is quite insignificant either as to general re- 

 sults or the projections of the Chart and Diagrams. 



