1850.] Nineteenth Memoir on the Law of Storms. 375 



curved considerably to the Southward and again to the North, to pass 

 as it did so close to the South of the Strabane, so as to bring the wind 

 from South to North West in 12 hours, and to depress her Barometer 

 from 29.50 to 29.40.* 



With regard to the rate of travelling we can only say that it seems 

 evidently by the short duration of that part of the Cyclone which was 

 of hurricane violence, and judging also from the estimated positions of 

 the centres on the 15th and 16th, and midnight of the 16th and 17th 

 that it cannot have been below 15 or 16 miles an hour. The rapid 

 and sudden fall of the Barometers of the Polly and Admiral Moorsom 

 within a short period shews that, for them, the more violent part was of 

 limited extent but proportionably severe. The Barometer of the Sir 

 H. Douglas did not indicate this peculiarity, but it may have been a 

 more sluggish instrument. 



A curious remark is made at the close of the Polly's Log, viz. that 

 the observations between the 15th and 19th shewed that the ship must 

 have been drifted four degrees to the Westward in the hurricane ! Now 

 this is scarcely possible, for the other ships would also have been 

 carried to the Westward and no doubt have noticed it, to say nothing 

 that the hurricane part of the storm did not last more than 24 hours 

 at most, so that we must suppose here a storm wave of 10 miles an 

 hour ! which is quite unprecedented. I should rather suppose some 

 error in the observations ? or that the Chronometer had been injured 

 during the Cyclone ? We must not forget however that this throws 

 much uncertainty on the Polly s position, and thus our track may not 

 have been quite so abruptly curved as we have made it. Yet it is 

 clear that we have yet much to learn regarding the tracks in this 

 quarter of the Ocean ; and such a one as is shewn by these ships' Logs 

 may doubtless occur, and the Mariner has here another caution when a 

 Cyclone is commencing with him. 



The Jumna's Cyclones. 



The following are the considerations upon which the track of these 

 Cyclones are laid down. 



* By a Barometer diagram which is sent with the extract the Barometer seems 

 to have been at its lowest at about 3 a. m. of the 17th (probably an error) though 

 the Log states it to have risen after midnight. The Simpiesometer both by the 

 Log and diagram appears to have been lowest at about midnight. 



3 c 2 



