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ON ATMOSPHERIC WAVES 



[Sect. X. 



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known tliat the oceanic surface, and even the smaller 

 surfaces of inland seas, produce decided inflexions of the 

 isothermal lines. They exercise an important influence 

 on temperature. It has also been shown that the neio-li- 



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boiirhood of water has a very considerable influence m 

 increasing the oscillations of the mercurial column in the 

 barometer, and in the great systems of European undula- 

 tions it is well known that these oscillations increase espe- 

 cially towards the north-west. The converse of this 

 however, has not yet been subjected to observation ; there 

 has been no systematic co-operation of observers for the 

 purpose of determining the barometric aifections of large 

 masses of water, such as the central portion of the basin 

 of the northern Atlantic, the portion of oceanic surface 

 between the Cape of Good Hope and Cape Horn, the 

 Indian and Southern oceans, and the vast basin of the 

 Pacific. Nor are we yet acquainted with the character 

 of the oscillations, whether increasing or decreasin^y, as 

 we recede from the central portions of the oceanic surfaces 

 we have mentioned towards the land which forms their 

 eastern, western, or northern boundaries. This influei 

 of the junction line of land and water, so fiir as it is yet 



known, lias been kept in view in framinc these instructions, 

 and 



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as it appears so prominently in Europe, it is hoped 



that additional observati 



ons betv/een the four dailv read- 



ings * to which probably many observers may habitually 

 restrict themselves, making on certain occasions and in 

 particular localities a series of observations at intervals of 

 three hours, will not be considered too frequent when the 

 reat importance of the problem to be solved is fully 



* See p. 271, 



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