LOW BAROMETER OF ANTARCTIC ZONE, 307 



Variation of mean barometric pressure, as we pro- 

 ceed from one place to another, may be due either to a 

 variation of circumstances of heat, moisture, and other 

 like relations, or to difference of level. Maury's ex- 

 planation assigns to the low antarctic barometer a cause 

 or causes falling under the former category. My theory 

 amounts to the supposition that the low barometer is 

 due to an absolute difference of level. I say that the 

 sea-level, to which we refer barometric pressure, is not 

 a just level of reference when atmospheric pressure over 

 the whole globe is the subject of inquiry, because the 

 southern seas stand out to a greater distance than the 

 northern seas from the true centre of gravity of the 

 earth's solid and fluid mass. 



Assuming my theory to be correct, we have a means 

 rough, it may be, but not uninstructive of deter- 

 mining the displacement of the centre of gravity of the 

 earth's solid mass from the centre of figure. For, accept- 

 ing one inch as the difference of barometric height at 

 the two poles, it is easily calculated that this difference 

 amounts to a difference of level of about 850 feet. In other 

 words, the surface of the water at the south pole lies 

 farther than the surface of the water at the north pole 

 from the centre of gravity of the entire fluid and solid 

 globe, by about 850 feet. Hence this centre of gravity 

 must lie about 425 feet north of C' (which is the centre 

 of the bounding surface of the water). Now, it is 

 evident that both the centre of gravity of the entire 

 fluid and solid mass, and that of the solid mass, must 

 lie much nearer to C than to C'. Hence both these 



