THE BUILDING OF THE EARTH 



is that owing to the distribution of its weight it is always 

 in what we call a state of strain ; and it is sometimes not 

 strong enough to support this strain, and, almost without 

 apparent cause, will sometimes give way. Much more 

 solid bodies than jelly act in the same way. The great 

 bridge near Quebec which collapsed in 1907 was to all 

 appearance quite sound and strong ; but there were strains 

 in the iron girders, and without warning these strains sud- 

 denly produced rifts in the iron and steel framework and 

 it broke down. Similarly the towers of churches and 

 cathedrals, which are built on arches, will give away 

 quite suddenly after standing to all appearance quite 

 firm for hundreds of years. There is an architect's 

 maxim which runs, "The arch never sleeps." That 

 means that the arches on which the great weight of 

 a church or cathedral tower rests are always in a state 

 of strain ; it is always, as it were, imperceptibly quiver- 

 ing ; and it is always liable, if the strain on it should be 

 increased in the slightest degree, to give way, or to try to 

 resettle the weight on its shoulders in some way. 



The whole of the great globe which we call the earth is 

 in this state of strain ; and it is always liable to rifts 

 within itself and to readjustments of the weights of its 

 own parts. It is not so easy to understand how a great 

 globe spinning through space can be in a state of strain, 

 or can attempt to readjust the weight of its parts, as in 

 the instances we have just given of the quivering jelly or 

 the solid cathedral tower. Perhaps another illustration 

 may help us. We will presume that nearly everybody is 

 acquainted with the modern rubber-cored golf ball. The 



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