148 HARBOUR CONSTRUCTION. 



not to prevent the broken water passing over into the harbour, 

 need not be carried much above the level of high water, and 

 could obviously be constructed for less money than one with 

 a costly superstructure. On the other hand, for a harbour of 

 refuge, where, in time of war, it might be of importance to ship 

 stores or material, and embark troops with rapidity, a break- 

 water with a vertical face, adequate depth of water alongside, 

 and a good sheltered quay, would possess great advantages as 

 compared with any of the forms of mound breakwaters, always 

 supposing that suitable inshore quay accommodation and other 

 facilities did not exist. 



When the area to be sheltered is such that vessels may be 

 expected to anchor, instead of being moored alongside of quays 

 or tightly packed together, as is too often the case in small 

 fishery harbours, the character of the bottom must be considered 

 with reference to its suitability, or otherwise, as holding-ground. 



Good holding-ground is that which is composed of tenacious 

 material such as tough clay or stiff silty sand sufficiently soft 

 to admit of anchors taking a good hold. 



Bad holding-ground is that where, as in the case of a rock 

 bottom, an anchor either cannot take hold at all, or, having done 

 so, probably takes such a good one that it cannot be got up 

 again. Loose material, such as clean shingle, through which the 

 anchor may draw, is also bad ; nevertheless, shingle mixed with 

 loamy sand l or other binding substance is often very good. 



Where holding-ground is bad, it will be necessary to lay 

 down moorings, secured by screws or in some other suitable 

 manner, according to the nature of the ground. 



Under Section ii. of the Report of the Sub- committee appointed 

 to investigate the question of the most suitable site for a harbour 

 of refuge on the east coast of Scotland (1884), the following 

 valuable and practical views are expressed in regard to the 

 leading requirements to be kept in view when choosing a site 

 for a harbour of refuge. 



" The term * harbour of refuge ' can be applied either in a 

 general or in a special sense. 



"A harbour of refuge, as understood in a general sense, should 

 be in a position in which vessels may obtain shelter under any 



1 There is a great difference in sands, some being so mobile as to afford scarcely 

 any hold at all, whereas others of a more silty nature are exceedingly tenacious. 



