82 HARBOUR CONSTRUCTION. 



through their roadways being ploughed out, these being too 

 often constructed, it may be, with only a thin skin of concrete, 

 or a foot or couple of feet of pitching, laid with open joints upon 

 a hearting of loose rubble. 



Fig. 15, p. 81, represents an action, going on at Holburn 

 Head, similar to that at Wick, as illustrated by Fig. 13. The 

 cliff at Holburn Head is, however, rriuch higher than that at 

 Wick, and the debris forming the mound is of much smaller 

 dimensions. 



The absolutely clean and new appearance of the rock surfaces 

 and of the debris at Holburn Head leaves no room for doubting 

 the statements made as to the winterly occurrence of storms 

 capable of performing such work. 



Examples from nature of what the waves of the sea can do 

 are of so much interest and value that I feel I need make no 

 apology for quoting at some length from Mr. Thomas Stevenson's 

 description of what he saw in Zetland. He states 



" On the south-east side of Bound Skerry, about 370 feet from 

 the low- water mark, and at a height of 62 J feet above its level, there 

 occurs a remarkable beach of angular blocks, varying in size from 

 about 9 tons downwards, and huddled together just as one would 

 have expected to find had they been elevated only a few feet above 

 the high- water level. 



" Towards the north-east, at the level of 72 feet above the sea, 

 in addition to many smaller blocks which had evidently been recently 

 detached, there was one 5 tons in weight. It presented the appear- 

 ance of recent detachment, having a fresh, unweathered look. Within 

 20 feet of the spot where it lay there appeared a comparatively 

 recently formed void in the rock, which, upon examination and com- 

 parison by measurement, was found to suit exactly the detached 

 block. Here, then, was a phenomenon so remarkable as almost to 

 stagger belief a mass of 5 tons not only moved at a spot which is 

 72 feet above high-water spring tides, but actually quarried from its 

 position in situ. But higher up still there was another detached 

 rock, weighing no less than 13 tons, tilted up in a peculiar position, 

 and underneath which numerous angular masses had been wedged, 

 obviously by aqueous action. This great block was, however, unlike 

 the one first described, in bearing no traces of recent displacement. 

 Though covered with lichen, and apparently long undisturbed, yet 

 there can be no doubt that it, too, had been separated from the parent 

 cliff, and been tilted up into the position which it now occupies by 



