BREAKWATER . When a See also:

• HARBOUR (from M.E. hereberge, here, an army; cf. Ger. Heer and -beorg, protection or shelter. Other early forms in English were herberwe and haiborow, as seen in various place names, such as Market Harborough.. The French auberge, an inn, derived through

Waves have been found to attain a maximum height of about to ft. in the See also:

• LAKE
• LAKE, GERARD LAKE, 1ST VISCOUNT (1744-1808)

A breaking wave concentrates its transmitted force on a portion of the water forming the undulation, which, consequently, strikes a more powerful blow over a limited See also:

• AREA

I). The flatness of the sea slope depends on the exposure of the site, and the limited size of the stones covering the outer portion of the mound; and its extent increases with the range of See also:

• TIDE (O. Eng. lid, cf. Ger. Zeit, time or season, connected with root of Sanskrit a-diti, endless)

3), and at the breakwater in deep water at Civita Vecchia, the concrete blocks covering the rubble have been laid in stepped, See also:

• HORIZONTAL

- tached breakwater, nearly 2 M. long, sheltering a very spacious harbour, was constructed in two years (1870-1872). Sometimes, when a mound breakwater has been raised out of water, See also:

• ADVANTAGE

See also:

• SPECIAL

At Marseilles, however, when the breakwater reached great depths, the quay was abandoned on account of the increased exposure, and the extension made of a simple rubble mound, protected on the sea side, from the top down to 20 ft. below sea-level, by large concrete blocks deposited at random. The superstructures at Holyhead and Portland, being built on the old weak system of a sea wall and a harbour wall, with rubble filling between, are protected on the sea side by raising the rubble against them from low water up to high water of See also:

• SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

The two old detached breakwaters sheltering See also:

• DELAWARE

A sheltering structure. wall was also generally erected on the sea side. This, for instance, was the system of construction adopted for the super-structures, founded at low water, of Holyhead breakwater, Portland inner breakwater, and St See also:

• CATHERINE
• CATHERINE, SAINT

The same form of superstructure, also, on a narrower base, was resorted to for a breakwater in deeper water at See also:

• SAN

The superstructures of the breakwaters forming See also:

• MADRAS

These, when settlement on the mound had ceased, were filled with concrete in bags, which not only connected the tiers of blocks in each section together, but also joined the several sections to one another, and effectually closed the transverse joints between the successive sections, which were further connected together by a continuous capping of concrete-in-mass along the whole length of the breakwater. These sloping blocks are laid by powerful overhanging, block-setting cranes, called See also:

• TITANS (Gr. Ttraaves)

Two circumstances, however, still render the composite form of break-water indispensable in certain cases: (I) the great depth into which breakwaters have sometimes to extend, reaching about 56 ft. below low water at Peterhead, and 102 ft. below mean sea-level at Naples; and (2) the See also:

• NECESSITY (Lat. necessitas)

In carrying out the work, however, the superstructure built in the summer months was for the most part destroyed by the following winter storms; and, accordingly, the superstructure was eventually constructed on a widened rubble base, so as to be sheltered to some extent by the outlying concrete-block mound already deposited, a system subsequently adopted in rebuilding the damaged portion of the North See also:

• PIER (older forms per or Pere, from Med. Lat. pera; the word for piers out of water. For river piers, where a firm, watertight is of obscure origin, and the connexion with Fr. Pierre, Lat. stratum is found at a moderate depth below the river-bed, the pctr

If a solid breakwater were erected on a soft yielding bottom, it would be exposed to dislocation from irregular settlement; and such a structure, by obstructing or diverting the existing currents, tends to create a scour along its base; whilst the waves in recoiling from its sea face are very liable to produce erosion of the sea-bottom along its outer toe. Moreover, when the foundations for an upright-wall breakwater have to be levelled by divers, and the blocks laid under water by their help, the extension of such a breakwater into a considerable depth is undesirable on account of the increased pressure imposed upon diving operations. The See also:

• ADMIRALTY, HIGH COURT OF

With a rise of tide at springs of 184 ft., the average depth is thus approximately 66 ft. at high tide, necessitating a pressure of 29 lb on the square See also:

• INCH (O. Eng. ynce from Lat. uncia, a twelfthpart; cf. " ounce," and see As)

Still later, the two break-waters sheltering the approach to the river See also:

• WEAR

In large structures, however, uniformity of design may be desirable for each straight length of breakwater; though where two or more breakwaters or outer arms enclose a harbour, the design should obviously be modified to suit the depth and exposure. At Colombo harbour, the superstructure of the less exposed north-west breakwater has been made slightly narrower than that of the south-west breakwater; and a simple rubble mound shelters the harbour from the moderate north-east monsoon. In special cases, where a breakwater has to serve as a quay, like the Admiralty pier at Dover, a high parapet wall is essential; but in most cases, where a parapet merely enables the breakwater to be more readily accessible in moderate weather, it would be advisable to keep it very low, or to dispense with it altogether, as at the southern Dover breakwater, the northern breakwater at Sunderland, and the Colombo western breakwaters. This course is particularly expedient in very exposed sites, as a high parapet intensifies the shock of the waves against a breakwater and their erosive recoil. Moreover, when a light has to be attended to at the end of a breakwater, sheltered access can be provided by a subway, as at Sunderland. Structures in the sea almost always require works of maintenance; and when a severe storm has caused any injury, it is most important to carry out the repairs at the earliest available moment, as the waves rapidly enlarge any holes that they may have formed in weak places. (L. F.