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I 



Sect. X.] 



AND BAR03IETRIC CURVES. 



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series of tliree-hourly observations may be commenced on 

 board vessels from America and the Pacific by tbe way 

 of Cape Horn on their passing the 20th meridian, such 

 three-hourly observations to be continued until the arrival 



of the vessels in port. 



Cap 



Good Hope should commence the three-hourly series 

 either on leaving or passing the colony, in order tliat the 

 phsenomena of the tropical depression hereafter to be 

 noticed may be well observed. 



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Northern Atlantic. 

 sailing to the United 



7 T 



Oviimrd-bound y 



States^ Mexico, and tne 



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es:;:ls 

 West 



Indies, should observe at three hours' interval upon pass- 

 ing the 60th meridian. Observations at this interval, on 

 board vessels naviofatins the Gulf of Mexico and the 



Caribbean Sea, will be particularly valuable in deter- 

 mining the extent of oscillation as influenced by the 

 masses of land and water in this portion of the torrid 

 zone, as compared with the oscillation noticed oft the 

 western coast of Africa, hereafter to be referred to. 



^ » 



Southern Atlantic. Outward and homeicard hound. 

 Without doubt the most interesting pbsenomenon, and one 

 that lies at the root of the great atmospheric movements, 

 especially those proceeding northwards in the northern 

 hemisphere and southwards in the south^.n, is the equa- 

 torial depression first noticed by Von Humboldt and con- 

 firmed by many observers since. We shall find the general 

 expression of this most important meteorological fact in tlie 

 Report of the Committee of Physics and Meteorology, 

 appointed by the Royal Society in 1840, as folio ws 







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