VARIOUS TYPES OP BREAKWATERS. 183 



All blocks should be laid as " headers." The smallest possible 

 surface will thus be opposed to the wave-stroke, the "scar end" l 

 of the work will be shortened, and the blocks will be less liable 

 to fracture by settlement than when " stretchers " are introduced. 



Batter in the faces of piers is objectionable, inasmuch as it 

 relieves the outer blocks of the lower courses from weight, and 

 necessitates a larger number of different-sized blocks being made 

 than would otherwise be required, thus involving extra expense 

 for moulds, etc. 



If desired, the outside blocks may be faced with stone on 

 their exposed faces, so as to enable them the better to resist 

 erosion. In such cases the stones should be properly bonded 

 and built into the block faces at the time the blocks are being 

 made, care being taken to ensure full beds and joints and a 

 perfect union with the concrete. 



A form of breakwater which has several points to recommend 

 it, especially for small or moderate depths of water, and where 

 the foundation is good, is one in which a base of mass-work is 

 brought up to slightly above the level of low water of neap 

 tides, the remainder of the work being carried up with concrete 

 blocks set in cement. By this arrangement the work may be 

 quickly raised above high water, and the risks inseparable from 

 the putting in of mass-work within the tidal range be to some 

 extent avoided. 



A type drawing of this form of breakwater will be found in 

 Fig. 32, p. 184. 



4. Breakwaters or Piers of Concrete Mass-work, deposited 

 within Temporary Frames. 



The monolithic system, already referred to, or that of forming 

 breakwaters by depositing freshly mixed concrete within tem- 

 porary timber frames, either under or above the water-level, is 

 applicable to large and small works alike, and may, if necessary, 

 be carried out with a very small expenditure on plant ; whereas, 

 if the magnitude of the work is such as to warrant the use of 

 plant on a larger scale, the rate of progress may be correspond- 

 ingly increased, and the cost of the work diminished. 



By this system the tedious and expensive operation of 

 accurately levelling foundations is to a great extent rendered 

 unnecessary, and large monolithic blocks may be constructed 

 1 The free end of a breakwater during construction. 



