Page:The New International Encyclopædia 1st ed. v. 03.djvu/511

BREAKWATER. 449 BREAKWATER. 1888 the structure had reached a lenjrtti of 2100 feet. Since 1893 work has been in |>ro<n'ess ex- tending this breakwater 580 feet, and in building a second structure of -similar type 1.500 feet long. The depth of water in which this breakwater is being built is about 4.5 feet. A conspicuous French example is to be found at Brest, the com- mercial harbor of which, completed about 1897, contains a breakwater half a mile long. NEW DELAWAUE BBEAKWATEH. Delaware Breakwater for the national harbor of refuge in Delaware Bay (U. S.) is IVi miles long, and is constructed in from 13 feet to 53 feet of water. It consists of a mound of rubble stone rising to low-water level, and above this of a rough wall of very large stones laid in courses without mortar, and with the interstices filled ■with small stone. This structure will shelter 552 acres with a minimum depth of 30 feet, and 237 acres with a minimum depth of 24 feet, the ■combined area being capable of sheltering 1000 vessels at once. The Sandy Bay Breakwater for the national harbor of refuge at Sandv Bay, Mass., begun in 1885 and still in progress (1901), will be 9000 feet long, and inclose an area of 1377 acres with a minimum depth of 24 feet. Below a point about 15 feet below low water this breakwater consists of rubble stones not exceeding in weight 4 tons each, and above this point it consists of stones weighing not less than 4 tons each, and averaging 6 tons each. The estimated cost of this brealcvvater is .$5,000,000. The breakwater at Point Judith. R. 1.. begim in 1890, and still in progress, will be 10,000 feet long, and is esti- mated to cost $1,200,000. It is being built of rubble stone to a dejjth of from 18 feet to 30 feet of water. The proposed breakwater for the deep-water harbor of San Pedro. Cal., will be 8500 feet long, constructed of rubble stone in water from 19 feet to 51 feet deep, and is esti- mated to cost $2,901,000. sisting of a concrete superstructure resting on a rublile-stone base. Several of the most important of these structures are brielly described in the accompanying table, rearranged from a table published by Mr. Louis Y. Schermerhorn, civil engineer, in a report to the United States Gov- ernment. The first five of these structures are of peculiar construction, in the respect that the concrete superstructure is built of blocks resting on the rul)ble base at an inclination from the vertical, and having their tops bound together by a super- imposed mass of concrete. This construction is supposed to permit the blocks to settle indepen- dently without destroying the integrity of the structure as a whole. The Presque Isle Point Breakwater, near Afar- quette, Mich., on Lake Superior, is a timber crib structure filled with stone. The cribs were each 24 feet wide and 50 feet long, and varied in LW. Cross Section PBESQUE ISLE BREAKWATER, LAKE StTPEHIOB. depth to suit the varying depth of water. These cribs were framed with solid 12 X 12-inch timber side walls, solidly bound together with 12 X 12- LOCALITY Base of Buper- Btructure below M L. W., feet Top of super- structure above M. L. W.. feet Total height of super- structure, feet Width of super- structure, feet Range of tides, feet Height above high water, feet Depth of water over site, feet Colombo, O».vlon. Indian Ocean Madras India Indian Ocean •20 22 tl8 15 t 16 22 22% t25 12 8 . J 20 9 12 10 ■"is 32 30 38 24 28 32 24 43 34 24 30 24 12-18 22-28 23 Vj 28-38 2.0 10 3.3 4.7 18-40 24-45 6.0 8.7 "i'.'s 6.5 14 0.3 12 10 1.5 12.5 20-28 18-.10 Kust.-ndl". ItuiEianIa, Black Sea Od'-^'^A ilUHHla Blfick Sea 12-20 •.'U-30 FluniH..^U8tria-HunK'.v. Adriatic Sea Tmuidun Holland Xorth Sea 20-70 10-30 • Rubble and in-ton bng» "f r oiicrete extend about 5 ft. above the base. T Reatace and sloix- iinitert.d with large <<>ncn-te blocks. J Includes a parapet 7 ft. high and 15 ft. thick. Before passing to a description of a few typ- ical breakwaters at the Great Lake ports in the I'nited States, some mention should be made of a mimber of important inean breakwaters con- inch cross-ties 24 feet long, running from wall to wall and dovetailed at the ends. Timbers 6 X 12 inches and 24 feet long tie the walls of the cribs lengthwise. These cribs were sunk close to-