THE BUILDING OF THE EARTH 



modern golf ball, as those who are aware who either 

 intentionally or unintentionally have cut through its outer 

 cover, consists first of a small hard core. Round this is 

 wound very tightly some two hundred yards of elastic. 

 The tighter this is wound the better, or at any rate the 

 more "bouncing" will be the resulting ball of india- 

 rubber elastic. But consider what is the usual condition 

 of this rubber- wound ball. Like our jelly it is always 

 in a state of stretch or strain. Even when covered with 

 the outer shell which completes the golf ball, the whole 

 ball is still, we might say, in a state of strain or tension. 

 That is one of the reasons why it bounces, and why it 

 flies better than the old solid ball off the face of a golf 

 club. But if you were to keep a golf ball for a hundred 

 years these strains in its interior would alter and adjust 

 themselves. One result would certainly be that the golf 

 ball might lose its elasticity. Another result would be 

 that its shape would slightly alter. 



Now a golf ball, however carefully it is made, is not 

 always evenly made. It weighs a little more on one side 

 than another; and the best golf balls, those which fly 

 truest and farthest, are those which are most evenly 

 made : so that we might say of them that the centre of 

 their weight was exactly the same as the centre of the 

 ball. If it is not, then the strains in the ball are always 

 pulling it a little more out of shape ; and the ball, as 

 golfers say, flies badly. Now the earth is like a badly 

 made golf ball. The centre of its weight, or, as we call 

 it, the centre of gravity, is not quite at the centre of the 

 earth. Moreover, owing to the enormous pressures which 



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