WAVE WORK 563 



the rate of erosion at different points which could be attributed to 

 variations in resistance of materials. 



An examination of the Seabright shore indicates that the greatest 

 damage to bulkheads resulted from the direct impact of the waves, 

 whereas the buildings suffered most from the undermining of the 

 ground upon which they stood. When it is remembered that ocean 

 waves strike a vertical face with a force of from a few hundred pounds 

 to more than six thousand pounds per square foot, their enormous de- 

 structive power may readily be appreciated. Solid blocks of granite 

 have been shattered by wave impact upon the coast of Holland, and 

 it is therefore not surprising that the wooden bulkheads of the Jersey 

 coast should yield to the attack of the sea wherever they were not rein- 

 forced by parallel rows of piling with heavy stone filling, or otherwise 

 rendered especially strong. Fig. 7 shows one of the weaker bulkheads 

 in the earlv stages of destruction. 



Most of the bulkheads were surmounted by a broad boardwalk which 

 served to shed falling wave crests back into the sea, and thus protected 

 the cliff from erosion. The force generated by masses of water falling 

 from the great height to which they are projected when a storm wave 

 strikes a vertical wall, may be sufficient to crush such a boardwalk, even 

 if supported by heavy timbers. During a severe gale at Buffalo, Xew 

 York, many large timbers, 12 X 13 inches in thickness, 12 feet long, 

 and 10 feet between supports, were broken like match sticks by the 

 impact of falling water which had been hurled from 75 to 125 feet 

 into the air by breaking waves. There are several localities in the Sea- 

 brigiit district where the demolishing of the bulkheads had been 

 hastened in this manner. 



Many of the bulkheads are protected by rows of piling set some dis- 

 tance out in the sea to break the force of the oncoming waves. Even 

 where the sea attack was powerless to break these pilings of to tear 

 them from their positions, the waves passed between the pilings and 

 still retained sufficient force to destroy the bulkheads which presented 

 a more continuous surface to their impact. Fig. 6 shows such a series 

 of protecting piling, which remained largely intact while the bulkhead 

 immediatelv in front of the house was battered down and the house itself 

 destroyed. Fig. 2 shows a series of pilings surmounted by undamaged 

 bath-houses, back of which the shore has been so badly eroded that the 

 superjacent houses have collapsed. 



As a rule, the houses were not damaged as much by direct wave 

 impact as by the undermining of the beach upon which they stood. It 

 is of course true that a building from under which most of the support 

 was already removed by the sapping action of the waves, often received 

 its "death blow" from some extra-large wave: and a l)uilding which 

 was once tipped over into the edge of the sea as a result of being under- 

 mined was soon pounded to pieces by the waves. The Octagon Hotel 



