VARIOUS TYPES OF BREAKWATERS. 175 



BREAKWATERS OF THE VERTICAL TYPE. 

 1. Timber Framing filled with Rubble Stone. 



Where suitable materials can be procured at reasonable cost, 

 pile-work breakwaters, with a hearting of rubble stone, may 

 often be constructed quickly, and at considerably less cost than 

 those built of solid masonry or concrete. Breakwaters of this 

 class have been constructed at Great Yarmouth, Boulogne, 

 Calais, Dieppe, Blyth, Dover (old harbour), Port Elizabeth, and 

 many other places. 



It may sometimes happen that the money available for 

 harbour improvements is insufficient for the construction of 

 what may be termed first-class works ; but it may, nevertheless, 

 if judiciously expended, be ample for works of a more temporary 

 nature, which will afford the requisite facilities for a time, and 

 possibly encourage trade and create a revenue, such as to admit 

 of their being improved or extended later on. In such cases, 

 breakwaters of the class we are now considering may often be 

 adopted with advantage. 



They are sometimes used for training the channels at the 

 mouths of rivers, and are suitable for this purpose when the 

 exposure is not great. 



Piers of this type were constructed at the mouth of the 

 river Wear upwards of one hundred years ago, and a portion of 

 the pier at Calais is of similar age. In the case of the Wear 

 breakwaters, the timber frames were put together on the land, 

 in lengths of 30 feet. They were then launched into the river, 

 and loaded with large stones to the extent requisite to give 

 them stability ; after which they were floated into position, and 

 sunk on the sand at about low-water level. Additional braces 

 and sills were then bolted on, and rubble filled in, the largest 

 of the stones being selected for building the inner and outer 

 faces of the pier. 



Breakwaters of this class are best suited for shallow water, 

 where they will not be exposed to very heavy seas. 



When the ground is suitable, the piles for such breakwaters, 

 instead of being framed together on land, as was done at the 

 Wear, are generally driven from an overhanging travelling stage, 

 the ties and bracings being fixed to them in place. 



It is very necessary, in constructing such works, to back up 



