arriving, consequently, except for differing coefficients K' and K at 



the same formula ,^' . _i 



/<, Ad 



(coset- s/r? <iJ3fe/-/)^ 



for the determination of the weight of the stones. 



There remains now only the determination of the coefficient K, or 

 K', and whether they remain constant or vary with the other elements , 

 of the formula o 



In the worst cases it is assumed that the variation of the coe- 

 fficient will be similar to that of the classic and variable coefficient 

 C of the formula of uniform movement 



c/= c/ri 



In order to test this assumption we have examined the coasts of the 

 Gulf of Vizcaya and found two locations suitable for the determination 

 of the coefficient K and a test of its constancyo 



These locations are the dikes at Orio and at San Juan de LuZo 

 The headland of the natural rock-fill dike at Orio is constituted of 

 compact sand stones about 3,000 kg in weight, with a density of d = 

 2„65 ton/m3„ 



At the completion of construction the headland had a slope of 1=5 

 horizontal to 1 vertical, which has been stabilized after the furious- 

 storms of recent years, on a slope of 3ol horizontal to about vertical 

 or 



coi a = 3.1 



giving 



The dike is founded on the sand of the beach at the level of 

 equinoctial low tide so that the maximum height of the wave which may 

 break against it approaches closely to the maximum depth at high tide, 

 or 4.o50 mo Waves of a maximum height of ^ = 50 m must have broken 

 against the headland since there have been most violent storms, coin- 

 cident with extreme tides, of several days duration during the past 

 yearo Applying the formula under these conditions, we haves 



Co. 95Z - 0. 306)^ (/. eS) ^ 



from which we obtain 



/<=/4.8 



The case of the Artha dike at San Juan de Luz is totally different. 

 Here the rock-fill is composed of blocks of concrete of i^ tons weight 



11 



