GEOLOGICAL CHANGES ON THE EARTH’S AXIS OF ROTATION. 
299 
deal, are competent to produce a geographical alteration in the position of the pole of 
between one and three degrees of latitude. But all these results are obtained on what 
I have called the hypothesis of incompressibility. 
Fig. 5. 
VI. HYPOTHESES OF INTERNAL CHANGES OF DENSITY ACCOMPANYING ELEVATION 
AND SUBSIDENCE. 
22. A general Shrinking of the Earth. 
It may be supposed that the earth is gradually shrinking, but that it shrinks quicker 
than the mean in some regions and slower in others. This would of course lead to 
depression and elevation above and below the mean surface in those regions. A defor- 
mation of this kind may be represented as a uniform compression of the earth, super- 
posed on changes such as those considered on the hypothesis of incompressibility. If a. 
be the coefficient of contraction of volume, it is clear that the values of D and E, as 
already found, must be diminished in the proportion of 1 — ~ to unity, and C — A must 
be diminished in the like proportion. Hence the deflections of the polar axis, on this 
hypothesis, are exactly the same as those already found. This seems, perhaps, the most 
probable theory, but it is well to consider others. 
The redistribution of matter caused by the erosion of continents will clearly produce 
the same effect as deformations on the theory of incompressibility. 
