VARIOUS TYPES OF BREAKWATERS. 



209 



(6) A mound of sorted rubble, of which the smaller sizes are 

 used to form the core, the larger being reserved for 

 the outer coating. This mound is capped by one of 

 pell-mell blocks, a layer or covering of which is also 

 carried down to the sea-bed on the weather side, so as 

 to entirely protect the seaward slope. The outer portion 

 of the breakwater at Algiers was constructed in this 

 manner. A typical section is given in Fig. 48. 



OFFING 



Fio. 47. Mound breakwater. Pell-mell blocks on rubble bue. Type (a). 



OFFING 



' - -TV >*^' - _-;.:.-..-/ -. 



FIG. 48. Ditto. Rubble, faced and capped with concrete blocks. Type (6). 



(c) A mound of pell-mell blocks, backed up on the harbour 



side by rubble, in order to prevent the passage of 

 undulations and silt, as was done at Alexandria (Fig. 

 49, p. 210). 



(d) A pell-mell block mound with a concrete or masonry 



superstructure erected thereon, as at Leghorn and St. 

 Jean de Luz (Fig. 50 ; p. 210). 



(e) A rubble mound with superstructure ; the seaward slope 



p 



TO 



-_ER1 



