8o 



HARBOUR CONSTRUCTION. 



above the sea, I cannot but think they must have been displaced 

 and arranged as they now lie *at a time when they were nearer 

 to the sea-level than they are at present, the land having been 

 subsequently raised. 



Be this as it may, instances of what the sea can do, and is 

 doing every winter, around the northern coasts of Scotland are 

 not wanting. 



Figs. 14 and 15 are from sketches which I made at Holburn 

 Head, near Scrabster, on the north coast of Caithness. 



Scale I inch = 80 feet. 



The excavation at A is in rock. 



It is 12 feet deep and about 38 yards across. 



FIG. 14. Sketch showing effect of falling water thrown up by storms at Holburn Head, Caithness. 



A more instructive example than that which nature affords 

 as illustrated by Fig. 14 of the effect of falling water upon 

 the roadway of a breakwater could scarcely be found. It was 

 largely due to this action of the waves that the breakwaters at 

 Alderney and Wick were laid in ruins, and it has been the 

 frequent cause of serious damage elsewhere. 



I was informed by the lighthouse-keeper at Scrabster, and 

 by others, that scarcely a winter passes without the occurrence 

 of one or more storms of such violence as to throw enormous 

 masses of "green water" high above the cliffs, which, falling as 



