342 



ENGINEERING. 



sure allowing the deepest piers to be sunk 4 

 feet into the bed-rock. The piers, when being 

 lowered were loaded with 150 Ibs. of ballast, 

 and when in place were filled up solid with 

 concrete. The swiftness of the currents and 

 the great rise of the tide prevented the ordi- 

 nary method of floating out the girders and 

 hoisting them upon the piers from being em- 

 ployed. They had, therefore, to be fitted to- 

 gether on the spot by the costly and primitive 

 method of working from scaffolds. The engi- 

 neers were George W. Keeling and George 

 "Wells Owen, with the consulting engineer, 

 Thomas K. Harrison. The amount of iron 

 used in the construction of the bridge was 7,000 

 tons. The formal opening took place on the 

 17th of October, 1879. 



The longest bridge in Europe will bo the 

 bridge now building over the Volga Eiver on 

 the Siberian Railroad in the government of 

 Samara, Russia. The river at the point crossed 

 by the bridge is 4 miles wide in the spring of 

 the year, and 4,732 feet wide in the autumn. 

 The part of the bridge which overhangs the 

 permanent channel will rest on 12 piers, 85 

 feet high, and placed at the distance from each 

 other of 864 feet. The estimated cost of the 

 entire structure is $3,500,000. Each pier is 

 guarded by an ice-cutter faced with granite, 35 

 feet high. Two thousand men are employed 

 in the construction of this colossal work, which 

 will be completed some time in 1880. 



Within the last dozen years American bridge- 

 builders have been carrying into practice 

 bolder and bolder plans, and have erected 

 works which far surpass in magnitude any- 

 thing attempted formerly. Such are Linville's 

 swing-bridge at Raritan, which turns on a col- 

 umn of masonry, and has a length of 472 feet; 

 the Rock Island swing-bridge, designed by 0. 

 Shaler Smith, which weighs 750 tons; and 

 bridges with draw-spans of over 360 feet on 

 the Mississippi. Such are the great channel 

 span over the Ohio in the new Cincinnati 

 bridge, which was also designed by Mr. Lin- 

 ville, and which is 520 feet long, and the main 

 spans of 300 to 400 feet in four other bridges 

 on the Ohio. Besides these extensive works, 

 which adhere to the ordinary types of con- 

 struction, entirely new forms have been devel- 

 oped for the achievement of engineering tasks 

 of even greater magnitude. Such are the steel- 

 ribbed arches for the St. Louis bridge, whose 

 three spans are each about 500 feet in length ; 

 such the stiffened suspension bridge at Pitts- 

 burgh ; and such the Brooklyn suspension 

 bridge with its steel-wire chords, its masonry 

 anchorage, and clear span of 1,600 feet. 



Both in Europe and America steel is coming 

 into favor as a material for bridges. The adap- 

 tability of steel for bridge construction is much 

 questioned by some engineers. The sudden 

 breakage of pieces of steel of a warranted high 

 degree of tensile strength, and the fact that dif- 

 ferent bars of high carbon steel, made from the 

 same materials by the same process, will differ 



in strength and elasticity, add an element ot 

 danger and uncertainty to the employment of 

 steel for bridges which is not encouraging. 

 Other engineers entertain no doubts or fears, 

 and would proceed at once to substitute steel 

 for iron in bridge-making. If there is any such 

 uncertainty in the strength and quality of steel, 

 it can doubtless be removed by improvements 

 in the process of the manufacture. The con- 

 struction of a bridge built entirely of steel, for 

 the Chicago and Alton Railroad, over the Mis- 

 souri River at Glasgow, Mo., marks a new de- 

 parture in American bridge -building. The 

 bridge was designed by D. D. Smith, who car- 

 ried on experiments for several years in the 

 commission of the United States Government 

 on the relative strength of iron and steel. The 

 project for this bridge is the result of the con- 

 clusion, to which his researches led him, that 

 steel bridges equal to iron in durability can 

 be constructed at a smaller cost. The bridge 

 has five spans of 314f feet each. Its eleva- 

 tion is 50 feet above high-water mark. The 

 quantity of steel used in the whole structure 

 was 1,500 tons, equal in strength to nearly dou- 

 ble that weight of iron. The girders are of 

 the Howe truss pattern. The structure, held 

 and braced in mid- air by slender steel rods, 

 presents a very frail and slight appearance, yet 

 it is able to bear a load which few iron bridges 

 could support. Three of the spans are above 

 the grade of the road, and two below. The 

 depth of the trusses is 36 feet from center 

 to center of the pins. The length of the steel 

 bridge is 1,573J feet. Including an iron tres- 

 tle 210 feet long, and two deck-spans of iron 

 140 feet each in the east approach, and an 

 iron trestle 510 feet long and wooden tres- 

 tle 864 feet long in the west approach, the to- 

 tal length of the bridge is 3,577| feet. 



In the Soodan Railway, which is to connect 

 "Wady Haifa, at the second cataract, with Khar- 

 toom, and thus bring the regions of equatorial 

 Africa into railroad communication with the 

 Mediterranean, the most important engineer- 

 ing task, the building of an iron bridge over 

 the Nile at Kohe", will soon be completed. 

 The contractors are Appleby Brothers, of 

 Greenwich, England ; the designs have been 

 drawn by the well-known engineer, John 

 Fowler. The point at which the railroad, 

 whose gauge is 3 feet 6 inches, is to be carried 

 over the Nile, is 1,170 miles above Alexan- 

 dria, and 750 miles below the confluence of 

 the White and Blue Niles. The length of this 

 railroad from "Wady Haifa to the terminus, 

 Khartoom, which is the chief emporium for 

 the products of Central Africa, is 560 miles; 

 the distance between the two places by river is 

 910 miles. The construction of the bridge in- 

 volves no engineering difficulties except such 

 as result from the distance of the site from civ- 

 ilization. The volume of water passing here 

 is even greater than it is at Kasr-el-Nil, 1,000 

 miles below, so much is lost by evaporation 

 and absorption, and so much is drawn off for 



