ENGINEERING. 



273 



iron path, and thousands upon thousands of 

 miles are already in contemplation ; while the 

 day may soon come when, like the Japanese, 

 the Chinese and the implacable nations of Cen- 

 tral Asia may open their inhospitable gates to 

 Western commerce and arts, and when the fer- 

 tile regions of inner Africa will be subjected to 

 cultivation, and whizzing trains will convey to 

 the sea-coast the precious materials which that 

 neglected region can produce. In the pause 

 which follows the, perhaps, too rapid extension 

 of railroads in the United States, the question 

 of the materials and modes of construction 

 which are most economical or secure, will be 

 more ripely considered. A greater uniformity 

 in the gauge will perhaps be arrived at after a 

 time ; many of the road-beds, as they need re- 

 pairs, will doubtless be more solidly rebuilt ; and 

 the question will present itself to railroad man- 

 agers, as to whether stone, when applicable, is 

 not a better, and really more economical, ma- 

 terial for bridges than iron, which requires con- 

 stant painting, and even then soon perishes with 

 rust, its tender joints and bolts being inacces- 

 sible to the painter. A more frequent use of 

 stone may be forced upon them by public opin- 

 ion, if criminal ignorance in construction, and 

 carelessness in examination, should result in 

 any more such disasters as that at Ashtabula. 



The new iron truss-bridge which is being 

 constructed over the gorge of the Kentucky 

 River is a remarkable structure, from the char- 

 acter of its site, and the novelty of its design 

 and mode of erection. The chasm over which 

 it suspends is 275 feet deep. The bridge will 

 be in 3 spans, 375 feet each, resting on the two 

 bluffs, and on iron columns, supported by 2 

 stone piers, 120 by 42 feet at the base. The 

 iron piers have 4 legs each, with a base of 71 

 by 28 feet, which come to a point at the end, 

 and terminate in a 12-inch pin, on which the 

 truss rests, as on a rocker ; the piers rest on 

 double roller beds, and can be moved about on 

 the masonry. The truss is a continuous girder, 

 projecting 75 feet at each end beyond its points 

 of support, with hinges to compensate the ther- 

 mal contraction and expansion of the iron 

 piers; it is 37 feet deep and 18 wide, each span 

 being divided into 20 panels. The ties, posts, 

 and chords are hinged on pin connections, while 

 the chords are riveted to each other, and the 

 pin carrying the tie-bars is driven into the chord 

 by hydraulic pressure, so that it partially serves 

 as a rivet. The bridge was built out panel by 

 panel, the support being the resistance of the 

 towers, built by Roebling for the projected sus- 

 pension bridge of 1,236 feet span, commenced 

 in 1854, and left incomplete in 1857, to the base 

 of which towers the top chords were fastened 

 by anchor-bolts, the lower chords resting against 

 the rock, to which they were forced by jack- 

 screws. The structure was thus held in mid-air 

 until it reached a temporary wooden tower, 

 196 feet 10 inches out, from the top of which 

 it was raised by huge jack-screws, until the 

 strain on the Roebling towers and anchor-bolts 

 VOL. xvii. 18 A 



was sufficiently relieved, when the work was 

 carried out in the same way to the top of the 

 first iron pier, 178 feet further. The work is 

 thus extended from either shore to the nearest 

 pier, and then from each pier to midway be- 

 tween them, where the two sections are joined. 

 There are 2,855,000 Ibs. of iron in the spans, 

 and 798,000 Ibs. in the piers; the masonry 

 measures 12,915 cubic yards. The engineer 

 who planned this important work is Shaler 

 Smith, of the Baltimore Bridge Company. 



The high truss-bridge over the Ohio River, 

 built for the Cincinnati Southern Railroad, was 

 tested on November 8th. It consists of 10 

 spans, 5 overhanging the river, and 5 the streets 

 and houses of Cincinnati. The river spans in- 

 clude one draw and one great channel span, the 

 longest in any truss-bridge in the country. The 

 river spans were built by the Keystone Bridge 

 Company, and the shore portion by the Balti- 

 more Bridge Company. The piers are all of 

 masonry, except one, which is of iron, resting 

 on a base of stone-work. The height of the 

 bridge, from top of rail to low-water mark, is 

 105f feet; the height above the mark of the 

 freshet of 1832 is 43 feet. The long span is 

 515 feet between the centres of the end piers ; 

 the depth of the truss is 51 feet. The two 

 trusses are divided into 20 panels of 25f feet 

 each ; their distance apart, from centre to cen- 

 tre, is 20 feet. The stone piers on which this 

 great span rests are, respectively, 119 and 110 

 feet in height, and are founded on the solid 

 rock ; their breadth at the top, below the cop- 

 ing, is 11 feet; their length 26 feet. The cost 

 of the structure was $700,000. 



A steel-wire suspension bridge is being built 

 at Cotteneva, in Mendocina County, Cal., 270 

 feet long, measuring from the centres of the 

 saddles on the towers. The cables are of No. 

 11 Birmingham wires, coated with zinc; 11 go 

 to the strand, and 7 strands to the 1^-inch 

 cables. The strands are not twisted together, 

 but gathered by bands 6 feet apart. The fall 

 of the cables is 23 feet. Each strand is tested 

 for a strain of 60 tons, and is fastened to an in- 

 dependent anchor-bar, and connected by 18- 

 foot links with the anchorage. The anchors, 

 of 1,000 Ibs., are imbedded 14 feet in the rock, 

 and secured by cross-beams, while the pits are 

 hemispherical, and the filling or stone-work, 

 set in Portland cement, is wedged against the 

 sides of the rocky chamber. The towers are 

 of red-wood. The dead weight of the bridge is 

 1,000 Ibs. per lineal foot; the strain for which 

 it is calculated is 7i tons per foot, or five times 

 the load to which it will be subjected. 



The use of malleable iron in girders is on the 

 increase. The bridge company in Canton, N. 

 Y., has the building of the new bridge over the 

 Connecticut, at North Hampton, 1,219 feet long, 

 with 8 spans, 18 feet roadway, contract $27,- 

 000 ; also a 6-span bridge, 930 feet long, and 16 

 broad, at Columbus Junction, la.; and one of 

 6 120-feet spans, at Paris, Ontario. They have 

 built, recently, a 160-feet span on iron piers, 



