Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/451

 BRONX,

THE -BROOKLYN 407 Bronx, The, the northernmost of the five boroughs account of the possibility of obtaining a material in which the elastic limit more nearly approaches the ultimate strength than is of New York city (q.v.) usually the case with bronzes. The composition -of manganese bronze in the ingot may be- taken as :—Copper, 56 52 per cwt. ; Bronze.—Bronze alloys have in recent years come tin, '85 ; lead, ’35 ; iron, 1 5 ; zinc, 4078, with a trace of manto be largely used in mechanical engineering. The prin- ganese. The fracture when broken by tension has a fine silky cipal bronzes are phosphor bronze, aluminium bronze, delta appearance. In the ingot the material may possess a tensile strength of 32 tons per square inch, with 35 per cent, elongation in metal, and manganese bronze. 2 inches, which is usually reduced by casting to about 29'5 tons per Phosphor hronze, in the ingot, has the composition—copper, square inch, with 20 per cent, elongation. By rolling, the tensile 87'8 parts; tin, 11‘17 ; phosphorus, 1'03, although this pro- strength is increased to 35 to 40 tons per square inch, with from portion may vary somewhat. After casting from the ingot, the 10 to 35 per cent, elongation in 2 inches. In casting there is phosphorus may be reduced to the merest trace, hut its presence considerable tendency to volatilize the zinc from overheating, while melting is useful. If overheated in casting, phosphor bronze rendering it somewhat difficult to secure sound castings with high loses many of its valuable properties. Phosphor bronze is used for tensional strength ; there is also a large amount of shrinkage in pump plungers, valves, bushes of bearings, &c., and generally for the mould when cooling, which is objectionable. Speaking generpurposes where a hard, strong metal is needed. It is less well suited ally, there is risk of unsoundness with liigh-tension bronze, rendering than other bronzes for bearing heavy vibratory loads. The tensile it somewhat untrustworthy for the purpose of retaining water or strength of phosphor bronze in the ingot ranges from 22 to 25 tons air under pressure ; but a low-tension bronze, with a tenacity of per square inch, with an elongation of from 4 to 8 per cent, in 2 about 12 tons per square inch, will give sound castings. Thus, a inches’ length. This strength is usually reduced in the casting to bronze composed of copper, 85'5 per cent. ; tin, 12'0 per cent. ; about 16 tons, and may be increased by the process of rolling to from zinc, 2'5 per cent., gives satisfactory results. (g. h. Ba.) 25 to 40 tons, with from 8 to 20 per cent, elongation in 2 inches. Brookfield, a city of Linn county, Mo., U.S.A., Aluminium hronze has a considerable tendency in casting to draw in the mould. It possesses a tensile strength of about 25 tons per situated in the northern part of the state, on the Chicago, square inch, with 17 per cent, elongation in 2 inches in the casting, Burlington, and Quincy railway, at an altitude of 757 and this may be further increased by rolling to 40 tons with 15 per feet. Population (1880), 2264; (1890), 4547; (1900), cent, elongation. This alloy will take a very high polish, and it is claimed for it that it does not readily corrode. It is difficult, if 5484. not impossible, to solder satisfactorily together articles made of Brookings, capital of Brookings county, South aluminium bronze. Bronzes termed Delta metal are variously composed to suit the Dakota, U.S.A., situated in the eastern part of the state, particular purpose for which the alloy will be used, and give on the Chicago and North-Western railway, and on Big generally excellent results. Some of these bronzes possess high Sioux river, at an altitude of 1636 feet. It is the seat of tensile strength and ductility. They resist corrosion from sea- the State Agricultural College. This institution, mainwater to a remarkable extent, and are well suited for manufacture tained at the joint expense of the state and the United of pump plungers, pistons, glands, and for screw propellers. Propellers of this material have in actual use withstood a re- States, had, in 1900, 29 instructors and 508 students. markable amount of deformation without fracture, while, on Population (1890), 1518; (1900), 2346. account of its malleability, a limited amount of bending of the BrOOkline, a town of Norfolk county, Massachusetts, propeller blade, resulting from accident, may be corrected by heating and setting. Delta metal heated to a dull red becomes U.S.A., adjoining Boston on the south-west. It is a malleable, and can be worked under the hammer, press, or stamps, residential suburb of Boston, containing several small the strength being very much increased by the process. When so villages, and is traversed by the Boston and Albany railway. treated an ultimate tensile strength of 30 tons per square inch has been obtained, with the remarkable elongation of 32 per cent, Population (1880), 8057 ; (1890), 12,103; (1900), 19,935. in 2 inches and a contraction of area of 30 per cent. Mr Alex. Brooklyn, formerly a city of New York State, Dick, of the Delta Metal Company, has made the discovery that copper and its alloys can be separated while in a heated and plastic U.S.A., but since 1st January 1898 a borough of the city condition, and, provided no air is allowed to come into contact with of New York. It is situated at the west end of Long the surfaces to produce oxidation, they will reunite under pressure, Island, in the south - eastern part of the state, and is becoming perfectly welded together. This has led to the laying separated from Manhattan borough, formerly New York down of plant for the manufacture of bronze tubes and pipes, and eity, by the East river. The borough of Brooklyn other sections, by the process of extension, the resulting products being of high quality and strength, and perfectly sound. The includes all of King’s county, the township of New Lots process of manufacture is carried on by means of a hydraulic press ; having been annexed to the then city of Brooklyn in 1886, the metal, which is at a high temperature, that of plasticity, about and Flatbush, Gravesend, New Utrecht, and Flatlands in 1000 deg. Fah., is placed in a compressing cylinder or container, into which the hydraulic ram enters. The ram is provided with a 1894. These additions gave the city an area of 65*77 dished steel check-disc at the forward end, which expands under square miles, extending from the East river across the the pressure and fits the bore of the cylinder. The die-plates are island to the south coast, and including the summer formed with openings representing the section required for the resorts of Coney Island. It retains under its present article to be produced, and in the case of tubes there is a mandril organization as a borough, practically the same area as it in the central opening in the die-plate, which is attached by ribs to the die. The plastic metal when flowing is divided by the ribs had before as a city. The borough contains thirty-two of the die, but becomes reunited and firmly welded together after wards. It is connected (1901) with Manhattan borough passing the ribs. This action is dependent on the exclusion of the by numerous ferries and by the Brooklyn suspension air. The process improves the quality of the metal, and some bridge, opened in 1883, and will in the near future be tests of delta metal bars made by extension show a tensile strength of 48 tons per square inch, with 32 per cent, elongation in 2 connected by additional bridges. Means of transportation inches. are ample; there are five lines of elevated railway, and The limit of elasticity of the alloys of copper and zinc increases there are trolley lines on many of the streets. The with the proportion of zinc. The amount of elongation before fracture also increases with the proportion of zinc, reaching a maximum at summer resorts on Coney Island on the south coast are 30 per cent, of zinc, and then decreasing rapidly. The tenacity in- connected with the city by trolley and steam railway creases with the proportion of zinc, attains a maximum at 45 per lines. The borough contains thirty-two parks, ranging in cent, of zinc, and then decreases rapidly. The alloys become size from a part of an acre to 516 acres, and with a total fragile when they contain 50 per cent, of zinc. By varying the proportion of zinc between 30 and 43 per cent, a series of alloys may area of 1027 acres; the principal and best known of these be prepared presenting very varied properties. The most malleable is Prospect Park, a little west of the centre of the borough, of -the series elongates about 60 per cent., with a tensile strength of containing 516 acres, and having the soldiers’ and sailors’ 17 5 tons per square inch. Higher tensile strength may be obtained memorial arch at its entrance. There is also Brooklyn by increasing the proportion of zinc, but the percentage of elonga- Forest Park situated in Queen’s borough, containing 535 tion is reduced thereby and the tendency to produce unsound castings materially increased. The addition of a small quantity of acres, and Fort Green Park in the heart of the city, iron improves the quality of copper zinc alloys. besides which may be mentioned in this connexion the Manganese hronze is a copper zinc alloy of high value, on beautiful Greenwood Cemetery, of 474 acres, and a number