ON ATMOSPHERIC WAVES 



[Sect. X. 



Sect 



Localities. — The three principal localities of storms 

 are as follows: — I. The western portion of the basin of 



the North Atlantic ; II. The China Sea and B 



ay of 



Bengal; and III The Indian Ocean, more particularly 

 in the neighbournood of Mauritius. The first two have 

 already been marked out as areas for the three-hourly 

 ohservations ; to the latter, the remark as to extra ob- 

 servations under the head of Desiderata will apply. 



Mr. Redfield has shown that on some occa- 

 sions storms have heen preceded by an unusual pressure 

 of the atmosphere ; the barometer has stood remarkably 

 hlgh^ and it has hence been inferred that there has ex- 

 isted around the gale an accumulation of air formino* a 

 margin ; barometers placed under this margin indicating 

 a much greater pressure than the mean of the respective 



localities. 



With regard to ih^ West Indian and Ame- 



rican hurricanes — any considerable increase of pressure, 

 especially within the space marked out to the eastward 

 of the 50th meridian, will demand immediate attention. 



Upon the barometer ranfrino- 



-"! 



very high within this 

 space, three-hourly observatioiis should be immediately 

 resorted to ; and if possible, hourly readings taken, and 

 this is thp more important the nearer the vessel mav be 

 to the oOth meridian. Each observation of the baro- 

 meter should be accompanied by an observation of the 



vf'ivA — its direction should 



be most carefully noted, and 



4 



the force estimated according to the scale in p. 300, or 

 by the anemometer. It would be as well at the time 

 to project the barometric readings in a curve even of a 

 rough cluaracter, that the extent of fall after the mer- 

 cury had passed its maximum might be readily discernible 



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