1845.] Thirteenth Memoir on the Law of Storms in India. 721 



knowledge ; but as this detail is necessary to a thorough understanding 

 of the subject by all, I cannot dispense with it. 

 The points for consideration then, are — 



1. The accuracy of the Charles Heddle's log as a whole, and in its 

 parts. 



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



3. The construction of the Diagrams in Plate II, from the log. 



4. The sizes and probable forms of the vortices round which she 

 scudded on different days, and her distance from the centres. 



1 . The accuracy of the Charles Heddle's Log, may certainly, I think, 

 be taken as being as great as the circumstances would allow. Captain 

 Finck is known at the Mauritius as an experienced and a careful sea- 

 man ; and to this indeed his log bears full testimony ; but there are 

 many circumstances which (on board a merchant ship particularly) would 

 unavoidably induce a less degree of accuracy than on board a man-of- 

 war in like circumstances ; and taking it that she was steered as cor- 

 rectly as a vessel could be steered in such weather, and perhaps even 

 from her fine qualities as a sailer better than some men of war, the 

 first question in the mind of a sailor is — "Yes; but how often was 

 the log hove in such weather ?" We should reply to this, first, that 

 in the hands of many (young) officers, in such weather, and when run- 

 ing from 10 to 13 knots, the common log is as liable to error even if it 

 was hove, as the guess of the experienced seaman. We have all known 

 a young, or a careless officer report a ship going nine, when she was go- 

 ing ten knots, and especially at night, when it is not easy for the person 

 heaving the log to have one eye, and a hand to the line, and the other 

 to the holder of the glass, who is often half asleep ; or on the other hand, 

 that a fault in paying out the line too fast, or want of quickness at the 

 glass or line may give eleven knots when ten or ten and a half are the 

 truth ; and in fact most seamen heaving the log really make their own 

 allowance for any deficiency or excess they may suppose from any 

 cause, and mark the run accordingly. I speak here of the common log 

 only, and not of the patent ones, which are doubtless far more correct. 

 But in the end, one error of our guess or measurement by log corrects 

 the other, and we may, I think, fairly say that, though doubtless in such 

 a hurricane of five days' duration the log was not hove with any regularity, 

 and especially during the night, yet the average of any day's run is not far 

 from the truth as to distance ? The latitudes as given are the next consi- 



