LOW BAROMETER OF ANTARCTIC ZONE. 291 



of the earth's mass as a whole, and presenting the 

 atmospheric feature in question as a statical one. 



The first theory I have to notice is one founded on 

 the configuration of land and water upon the northern 

 and southern hemispheres of the earth's globe. In the 

 northern hemisphere, and more especially in that part 

 of the northern hemisphere in which barometrical 

 observations have been most persistently and systemati- 

 cally conducted, there is much more land than in the 

 southern hemisphere. Now barometrical observations 

 are referred to the sea-level, and observations made in 

 Europe and America may be considered as referred to 

 the level of the northern parts of the Atlantic Ocean. 

 It is argued that the North Atlantic, compared with 

 southern oceans, is little more than ( a large lake, having 

 elevated banks east and west.' ' Practically, the air 

 there is a portion of the solid globe, so that the uncon- 

 fined air will rest upon and rise above the former, as if 

 it were solid and a portion of the earth ; so that the 

 altitude of the air over the North Atlantic will be in- 

 creased some hundreds of feet, and the barometer at 

 the sea-level will be pressed upon, not only by the free 

 air clear of the earth's banks, but also by the air con- 

 fined in the basin, much as if the air were at the bottom 

 of a mine.' ! 



Presented in the above form, the theory that the 

 higher northern barometer is due to the contour of the 

 northern hemisphere scarcely deserves serious comment. 



1 From a letter addressed to the editor of the Athenaum by Dr. H. 

 Muirhead. 



u 2 



