RATE OF BEOSION OF THE SEA-COASTS OF ENGLAND AND WALES. 921 



I have directed my attention to three modes of protecting this work, viz., by an 

 extension of the system of groynes, the abandonment of the present breakwater, and 

 the construction of an inner sea wall nearer the redoubt, intersecting the counter- 

 scarp wall, and the strengthening and maintaining and extending the present sea 

 face, and am induced to recommend the latter course. 



There arc, however, it appears to me, serious defects of construction in the present 

 breakwater, and I will lirst describe the state in which I found it, and what appear 

 to me to be the causes of its failure. These my inspections will enable me to do, as 

 the western or southern half remains entire, and the eastern or northern half has 

 been breached over almost its entire surface, exposing to view the debris of former 

 defences, on which the present have been founded. 



The glacis of the redoubt appears formerly to have been formed of shingle and 

 earth coated with clay and grass-grown. As this became abraded by the sea, con- 

 sequent on the recession of the shingle, a system of defence was adopted known along 

 the coast as ' arming,' faggots being driven down over the surface of the slopes, 

 holding down watlings by means of overlaths. Many of these old and decayed 

 faggots may be seen at the present time in the breach, and this is one of the defects 

 of this work — that succeeding defences have been added and placed above the old 

 ones without removing them or obtaining a sufficiently solid base. As these old works 

 have decayed they have subsided and left vacuities under the modern works. This 

 remark applies to the timber wharfing or bulwark of the apron or breakwater erected 

 80 recently as the summer of 1 856, formed of whole timber piles 22 feet long, which 

 are now, in places, exposed nearly half their length, driven 4 feet apart, alternately 

 in front and to the rear of 4-inch horizontal planking, backed with 4 feet of block 

 concrete, the outer piles being held back to land-tie piles only 4 feet back in the 

 rear of the concrete ; and it appears that behind all there is an old timber breast- 

 work. Ihe angular space between the old slope, the outer breastwork, and the surface 

 of the present slope is formed of shingle covered with concrete, which receives the 

 stone paving or brickwork, as it may be. Through this shingle substratum the sea 

 must percolate freely. This is seen now at low water by the great quantity of water 

 running out through the bulwark and gulling out a small run of water across the 

 shore just east of No. 5 groyne, which has previously been penned up after high 

 water in the breached portion. AV'hen the general character of the work is considered, 

 the constant infiltration of the sea has been one of the causes operating in producing 

 settlement, in addition to the decay and subsidence of the materials of former works ; 

 added to this, the timber breastwork, when exposed to the impact of the sea towards 

 high water by the removal of shingle usually lying against it (which is its present 

 condition, consequent on the late easterly gales), is not of a nature to resist effectually 

 the enormous force brought to bear immediately against it, which, during my visit, 

 caused a sensible vibration through the whole mass of the breakwater, and threw up 

 a column of water about 30 feet high. Where the bulwark projects above the shore, 

 an overfall is created on the receding of the wave, tending to scoop out the shingle. 

 This applies to the east and west ends. Where the shingle is level with the top at 

 the south-east end the sea runs over without breaking. The brickwork forming por- 

 tions of the slope laid in the summer of 1856 is much worn from the abrasion caused 

 by the shingle dashed against it at high water, and the concrete slope above appears 

 very doubtful, having apparently swelled upwards in places, and sounds quite hollow 

 to the tread. The manner in which the breastwork springs or yields back and then 

 forwards, consequent on the removal of the shingle in front of it, by which the weight 

 of the material of the glacis is brought to bear against it, has been well described in 

 Captain Baillie's report. This produces a loosening of the stones of the slope at the 

 joints, which are subsequently readily removed by the sea. During my visit, by the 

 settlement outwards of the breastwork, the main longitudinal joint between the 

 marginal stones and pitching required pointing, as also some of the main longitudinal 

 joints up the slope ; and along the south-west frontage the coping stones had settled 

 Tertically, leaving the brick projecting, and which may thus be readily under- 

 mined. 



Where exposed, the breastwork is being strengthened at the most projecting 

 angles seaward by open piled and braced counterforts, to counteract the tendency it 

 appears to have to settle outwards consequent on the removal of the shingle. The 

 same thing has taken place vnth the old south timber revetment, which has settled 

 outwards, and is much out of line with an intervening space between it and the con- 

 crete backing. It is possible that the free admission of water into the foundation of 

 this work, the paving having close joints, with a homogeneous body below for a 



