12 ABOUT VOLCANOS AND EARTHQUAKES. 



they will rise ; if the bed of the sea receive additional 

 weight, it will sink. The bottom of the Pacific is sink- 

 ing, in point of fact. Not that the Pacific is becoming 

 deeper. This seems a paradox ; but it is easily explained. 

 The whole bed of the sea is in the act of being pressed 

 down by the laying on of new solid substance over its bottom. 

 The new bottom then is laid upon the old, and so the 

 actual bed of the ocean remains at or nearly at the same 

 distance from the surface water. But what becomes of 

 the islands 1 They form part and parcel of the oU 

 bottom ; and Dr Darwin has shown, by the most curious 

 and convincing proofs, that they are sinking, and have 

 been sinking for ages, and are only kept above water by 

 what, think you ? By the labours of the coral insects, 

 which always build up to the surface ! 



(18.) It is impossible but that this increase of pressure 

 in some places and relief in others must be very un- 

 equal in their bearings. So that at some place or other 

 this solid floating crust must be brought into a state of 

 strain, and if there be a weaK or a soft part, a crack will 

 at last take place. When this happens, down goes the 

 land on the heavy side, and up on the light side. Now 

 this is exactly what took place in the earthquake which 

 raised the Ullah Bund in Cutch. I have told you of a 

 great crack drawn across the country, not far from the 

 coast line ; the inland country rose ten feet, but much of 

 the sea-coast, and probably a large tract in the bed of 

 the Indian Ocean, sank considerably below its former 

 level. And just as you see when a crack takes place in 

 ice, the water oozes up ; co this kind of thing is always, 



