Page:The New International Encyclopædia 1st ed. v. 03.djvu/510

* BREAKWATER. 448 BREAKWATER. struction was teguu in ITSfiSS by sinking 18 timber frustums of cones liiiving a diameter of 142 feet at the base and 113 feet at the top. and a vertical height of 65 feet, which allowed them CHEBB0UB6 (FKANCE) BREAKWATER. to project from 6 feet to 10 feet out of water when sunk. These timber frameworks were sub- merged at irregular intervals by filling tliem with stone, so that they formed a row nearly 2V-> miles long. About 3.703,703 cubic yards of loose stone were deposited in and around these cones. This original construction cost about .$4,512,200, but the experiment proved unsuccessful, as the cones were battered into pieces by the waves, leaving only a series of mounds of loose stone, the tops of which were eventually below water- level. The work remained practically in this con- dition until 1830, when it was decided to make the loose stone mounds continuous by filling be- tween them, and to construct on this ridge a masonry all rising from low-water level, 36 feet 3 inches wide at the bottom and 20 feet 3 inches high, and 8 feet 3 inches wide at the top. It was built of rubble masonry, with a dressed stone facing. Since the construction of this original wall considerable work has been done in the way of strengthening and raising the rubble base and the wall. Plymouth Sound or Harbor, being open to the sea, was so much exposed to stcuins that early in the last century it was determined to construct a breakwater across its mouth, with openings between it and the shore on either side, for the ingress and egress of shipping. The works were commenced in 1812. The operations consisted in transporting along a tram-road large blocks of limestone procured from a neighboring quarry, shipping them in vessels fitted with trap-doors, and depositing them in the shajjc of a huge mound in the recpiircd situation. As soon as the stones began to a])pear al)ove water, a per- ceptil)le benefit resulted in the relative calmness of the Sound during the prevalence of storms: but the structure was frequently very roughly PbYMOUTB (ENO.) BBEAKWATEB. handled by the waves, which altered and flat- tened its shape. A severe storm in November, 1824, tlirew a great portion of the stones over into the Sound. It was not until 1841 that the works were finally completed by the deposition of more than 3,000,000 tons of stone, and the total ex])enditure of nearly .$7,.')00,00. The breakwater is nearly a mile long; the central i)or- tion is 1000 yards; and two wings of 3.50 yards each extend from tlu' ends of this at a slight angle. The open chaniuds at each end, between the breakwater and the shore, are each aliout half a mile wide, and their depth is respectively 40 and 22 feet at low water. The breakwater is 133 yards wide at the base, and 15 at the top, the two sides being made very sloping for the security of the stones. The slopes and top are faced with masonry.' The water-space protected by tliis breakwater comprises 1120 acres. To convert Holyhead Bay, Wales, into a har- bor of refuge, an attached breakwater 78U0 feet long was constructed, consisting of a loose stone base capped by a wall of solid masonry about 40 feet high, and, including th<! 40 feet wallway, about 60 feet wide. The method of construction was to convey the stone quarried from Holyhead Mountain out on a trestle in cars and dump it into the sea luitil the mound reached the proper BOLVHEAD (WALES) BREAKWATER. height. To form the sea end or head of this breakwater, a masonry platform 50 feet wide and 150 feet long was constructed, and im it a light- house was erected. The breakwater was begun in 1847 and finished in 1873 at a cost of over $815 per linear foot. This breakwater incloses an inner harbor of 207 acres and shelters an outer roadstead of 400 acres. The Portland (England) Breakwater was built to convert the expanse of water between the Eng- lish mainland and the isle, or rather the penin- sula, of Portland into a harbor of refuge. An act of Parliament was obtained in 1847 author- izing the work. The breakwater, starting from the northeast point of the isle, stretches nearly due north for more than 8100 feet, with one in- tervening opening 400 feet long for the ingress euUTI.ANll (KN(i.) BKKAKWATEIl. and egress of shipping. The works were con- ducteci more easily than those of any other great breakwater, for the isle contains an abundance of stone easily (|uarried, anfl flic steep sh<n"es afford- ed facility for trans])orting the stones by their own gravity to their destination. The work, which is an upright ashlar su|ierstructure, with a parapet founded on a mound of rubble stones, was done chiefly by convict labor; the depth is abcmt 50 feet at low water. From tlu- nature of the operation, any part of the breakwater be- came useful as soon as constructed. The width of the rubble mound at the bottom is 340 feet. This breakwater was constructed between 1849 and 1871, and contains a volume of 4,245,185 (■ibie yards of rul)ble stone. Dover Breakwater, in England, is particularly interesting as l)eing built of solid masonry throughout, the work under water being done by divers. The interior oi the structure consists of concrete blocks and is faced with cut stone masonry. The work was begim in 1847, and in