Masterpieces of Science 



wall, but the church, which in the time of Henry 

 VIII. was nearly a mile inland, is now on the very 

 brink of the cliff; and, indeed, it has only been 

 saved from actual destruction by artificial means. 

 As the two towers of the church form a well- 

 known landmark to mariners, a causeway has 

 been constructed on the beach to arrest the 

 progress of the sea. 



If the sea were a body of water in perfect re- 

 pose, it would be utterly incapable of effecting 

 mechanical erosion. But everyone knows that 

 the sea in never absolutely at rest, and that, even 

 in calmest weather, its surface is ordinarily more 

 or less troubled with waves. It is easy to 

 understand how these are formed. When you 

 blow upon the surface of a basin of water, the 

 mechanical disturbance of the air is immediately 

 imparted to the liquid, and the surface is thrown 

 into a succession of ripples. In like manner, 

 every disturbance of the atmosphere finds its 

 reflex on the surface of the natural waters. Each 

 puff of wind catches hold of the water, and heaps 

 it up into a little hill with the face to leeward; 

 then the crest falls, and the water sinks down 

 into a trough, as deep below the mean surface as 

 the hill was high above it; but the next column 

 of water is then forced up, only however to be 

 pulled down again, and in this way the motion of 

 the wave may be propagated across a broad ex- 

 panse of water. Drop a stone into a pond, and 

 the same kind of action will be seen; the water 

 all around the spot where the stone falls is first 

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