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Sect. X.] 



AND BAEOMETRIC CURVES. 



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by the eye. A paper ruled in squares, the vertical lines 

 representing the commencement of hours, and the auri- 

 zontal tenths of an inch, would be quite sufficient for this 

 purpose. The force of the wind should be noted at, or as 

 near to the time of the passage of the maximum 

 possible. Durir 



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the fall of the mercury particular 

 attention should be paid to the manner in which the wind 

 changes, should any change be observed ; and should the 

 wind continue blowing steadily in one direction, but gra- 

 dually increasing in force, then such increments of force 

 should be most carefully noted. During the fall of the 

 barometer, should the changes of the wind and Its in- 

 creasing force indicate the neighbourhood of a revolvino- 



torm, (independent 



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the focu 



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) 



reasons for avoiding 



to 



increase our knowledge of these dangerous vorticos 

 keep as near as possible to their margins as to approach 

 their centres. The recess from the centre towards the 

 margin of the storm, will probably be rendered apparent 

 by the rising of the mercury, and so far as the obser- 

 vations may be considered valuable for elucidating the 

 connection of atm.ospheric waves with rotatorv storms 

 (other motives being balanced), it might be desirable to 



margin— provided she is not 



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keep the ship near the 



c^irried beyond the influence of the winds which charac- 

 terize the latter half of the storm— until the barometer 

 has nearly attained its usual elevation. By this means 

 some^ notion might be formed of the generaf direction of 

 die nne of barometric pressure preceding or succeeding 

 a storm. 



Should a gale be observed commencing withou 





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