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338 



ON ATMOSPHERIC WAVES 



[Sect. X. 



liavin^ been preceded by an unusual elevation of tlie 

 mercurial column, and consequently no additional obser- 



made ; wben the force of the wind is 



een 



ration have b 

 noted in the usual observations at or above 5, then the 



series should be resorted to, and the same 



_^ 



tliree-hmirly S( 



care taken in noting the direction, changes, and force of 



the wind as pointed out in the preceding paragraph. 



The foregoing remarks relate especially to the central 

 and western nortions of the North Atlantic ; they will 

 however equally apply to the remaining localities of 

 storms. Under any circumstances, and in any locality, 

 a Mf/h barometer not less than a low one should demand 

 particular attention, and if possible, houriT/ readings taken 

 some time before and after the passage of the maximum : 

 this will be referred to more particularly under the next 



Preceding and Succeeding Accumulations of Pressure. 

 Mr. Redfield has shown in his Memoir of the Cuba Hur- 



ricane oi Oc 



f 



tober, 1844, that two associated storms were 

 immediately preceded by a barometric wave, or accumu- 



lation of pressure, the barometer rising above the usual 



or annual mean. We have just referred to the import- 

 ance of hourly observations on occasions of the readings 

 being high as capable of illustrating tlie marginal phe- 

 nomena of storms, and in connection with these accumu- 

 lations of pressure in advance of storms we woidd reiterate 



the suggestion. These strips of accumulated pressure are 



doubtl 





crests of atmospheric waves rolling forward 



s. 



In some cases a ship in its progress may cut them trans- 

 versely in a direction at right angles to their lengthy m 

 others very obliquely ; but m all cases, whatever section 



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