Page:The American Cyclopædia (1879) Volume III.djvu/245

 BREAKWATER BREAM 239 superstructure of these works were received and placed in position, completing 120 running feet of the breakwater and 175 feet of the ice- breaker. In addition, 122 tons of old super- structure have been reset and 2, 198 perches of small stone deposited in holes at the extremities of the works and on the sea side of the break- water opposite the lighthouse. The length of the breakwater on the top is 2,558 ft. ; about low-water line the length is 2,603ft.; length at base, 2,763 ft. The length of the ice-breaker as completed on the top is 1,353 ft. ; about low-water line, 1,389 ft. ; length of base, 1,601 ft." Col. Kurtz in his .report for 1871 says: "The completion of this harbor according to the original project was reported in last year's annual report. This project was devised more than 40 years ago. It is the case here, as in many other government works, that the growth of the country has far exceeded the provision made for its probable wants. Last year's re- port shows that 15,000 vessels were recorded as visiting this harbor. Adding those enter- ing and leaving without being noted, 20,000 or 25,000 may be taken as the number that used the harbor during the year. Its present capa- city is determined by the space that is sheltered by the breakwater proper. This is a straight line nearly half a mile long, and may be taken as the diameter of a half circle behind it, the area of which will represent approximately the sheltered harbor. Northeastwardly of the breakwater is the ice-breaker structure, a quarter of a mile in length, but separated by a gap of nearly equal extent, through which the sea rolls in northwestwardly weather without hindrance. If this were excluded, the sheltered area would be increased three or four fold." Col. Kurtz then presents the plans of Major Bache enumerated above, but is obliged to greatly increase the estimates of cost, viz. : for the first plan, $1,314,000; for the second, $1,944,950; and for the third, $2,278,000. The existing works have cost $2,127,403. A special board of officers, composed of Gens. Woodruff, Wright, and Newton, and Cols. Kurtz and Oraighill, appointed for the pur- pose of considering the question of further improvements to the breakwater, met in No- vember, 1871, and again in the summer of 1872. At the latter meeting a report was agreed upon favoring the plan of connecting the two moles by extending the breakwater proper until it meets the ice breaker. Break- waters are now in course of construction on our northern lakrs, which are made of a crib- work of strong timbers filled with stone, and are found to be very effective, and to possess the advantage of economy and facility of con- struction. It has been found by experience that the cribs will keep in position better if the bottom is formed of latticework, sufficiently open to allow the stones to sift through when the crib is stirred by the waves. The cribs are usually made from 30 to 40 ft. in width, from 60 to 80 ft. in length, and of a depth suited to 119 VOL. HI. 16 the depth of water. They are successively sunk and placed end to end and tilled with stone until the work has attained the desired length. There being no tide in these lakes, the I top of the crib need not be more than 8 or 10 ! ft. above the mean water level. Such break-
 * waters, more or less approaching completion,

j are in process of construction at Buffalo on j Lake Erie, at Oswego on Lake Ontario, at Plattsburgh and Burlington on Lake Chmn- plain, and at other places. Aside from not possessing sufficient strength, these structures would not be practicable on the seacoast on account of the destruction to which the timber worms ; but in our fresh-water lakes this ob- I jection does not exist. Timber which is placed ] below the action of the air in fresh water has
 * would be exposed from attacks of marine
 * been found to resist decay for an indefinite

time, for centuries at least. If from any cause, however, the framework of the cribs should become weakened, new cribs can be placed on the inner or outer line of the first row, or on both sides, and thus a permanent stone founda- tion of rubble for a stone breakwater of the ordinary description may be gradually con- structed. The experience acquired by all these breakwaters, and by the action of the waves upon coasts exposed to their greatest violence, establishes the principle that blocks of stone of large dimensions only can be depended upon to retain their places. Mr. James Walker, presi- dent of the British institution of civil engineers, advanced the opinion in 1841 that a partial vacuum is created by the action of the waves, and the atmospheric pressure being taken off for an instant, the mass of stone is the more readily influenced by the forces which at the j same time solicit it. ("Civil Engineer and Architect's Journal," September, 1841.) If the whole atmospheric pressure were taken off the surface, it would be equivalent to the removal of a weight represented by a column of rock 11 ft. deep, weighing 175 Ibs. to the cubic foot. Under such circumstances, and exposed to the action of a wave 20 ft. high, which is capable of moving masses of rock 7J ft. deep, stability would be insured only by the addition of this amount to the 11 J ft. But as it is not probable that a large proportion of the at- mospheric pressure is ever thus removed, and as 22 ft. is regarded as the maximum height of waves, a depth of solid stone of 15 ft., used as a coping, would probably resist all action of the waves. The construction and history of the principal breakwaters are fully treated in the great work of Sir John Rennie, president of the institution of civil engineers, upon Brit- ish and foreign harbors (2 vols. fol., 1854). BREAM (pomotisvulgaris, Cuv.), an acantho- pterygian fish, of the family pereida, of which several species are found in North America, and of which the above, called also sunfish, pond perch, and roach, is the most common. In this genus the borders of the preoperculum have a few denticulations ; no teeth on the