ENGINEERING. 



245 



road conveyance. On the strength of this in- 

 formation the French Government resolved on 

 the gradual improvement of harbors, rivers, 

 and canals, the total expenditure determined 

 on for this object being $200,000,000. The 

 scheme of a ship-canal, connecting the Atlan- 

 tic and the Mediterranean, to save the long 

 and perilous voyage around the Spanish Penin- 

 sula, is still under consideration, and has good 

 prospects of being adopted. 



The Dutch have been stimulated, by the de- 

 flection of the Rhine-trade to Antwerp, to im- 

 prove and expand their canal system, which 

 has been for centuries the world's model. 

 The States-General of Holland recently voted 

 $1,250,000 for improving the canal from Rot- 

 terdam to the sea, and decided to cut a new 

 canal from Amsterdam to Utrecht, and thence 

 to the Merwede River, near Gorcum. The citi- 

 zens of Amsterdam propose to construct an- 

 other one between their city and the Waal, 

 through the Guelon Valley. The Belgians are 

 not disposed to yield up the prize without a 

 contest. The canal at Charleroi is being wid- 

 ened, and a large central canal is to be dug 

 through the whole breadth of the country. 

 The Government is attempting to establish 

 uniformity of gauge in the canals of Belgium. 



The great suspension-bridge across the East 

 River, in New York, is nearing completion. 

 The year has seen the approaches substantially 

 finished and the work on the superstructure 

 begun. Nearly all the floor-beams were laid 

 before the close of 1881. The original plans 

 were materially changed during the year, mak- 

 ing the bridge five feet wider and four feet 

 higher above the river, with greatly increased 

 strength, to enable it to carry railway-trains of 

 Pullman cars. 



The tunnel under the Hudson is progressing 

 rapidly and securely by improved methods, 

 work going on from both shores. Steady prog- 

 ress has also been made in the excavations 

 under Hell Gate for the removal of Flood 

 Rock. Safety in the navigation of New York 

 Harbor and adjacent waters has been largely 

 enhanced during the year by the introduction 

 of iron-hulled passenger and excursion steam- 

 ers. 



The renewal of the suspension-bridge at Ni- 

 agara is a remarkable feat of engineering skill, 

 as all the parts of the structure were removed 

 and replaced with new, except the cables, 

 which were repaired at the shore-ends, and a 

 new anchorage was made, without any inter- 

 ruption of the railroad traffic. The fact that, 

 after twenty -five years of use, the wire cables 

 and suspenders of this gigantic span were 

 found but very slightly impaired, is a gratify- 

 ing proof of the security and durability of this 

 type of structure. In 1877 Thomas F. Clarke 

 examined a portion of the strands imbedded 

 in the masonry, and found a few wires cor- 

 roded. W. H. Paine shortly afterward insti- 

 tuted a more thorough investigation. Tests of 

 the elongation of the cables under a given 



moving load, and tests of single wires for ten- 

 sile strength and ductility, were satisfactory. 

 The strands were cleaned, freed from the wire 

 bands, and opened, with the result of finding 

 them as good as new, with the exception of 

 the outer wires of the outside strands. As the 

 shores were approached only the strands under- 

 neath were found to be affected. It was seen 

 that the corrosion was due to the fact that the 

 elongation and contraction of the strands un- 

 der passing loads had loosened the cement 

 from the outside strands, and allowed moisture 

 to enter. The defective wires were cut out 

 and new ones spliced in. The greatest num- 

 ber replaced at one end of any one cable was 

 65, the total number comprising each cable 

 being 3,640. The examining commission rec- 

 ommended that the anchorages be re-enforced 

 and that the iron superstructure of the bridge 

 be renewed, and reported that the action of 

 the cables indicated that they were in perfect 

 condition. In the plan which was executed for 

 the strengthening of the anchorages, one an- 

 chor-plate in each pit is made to answer for 

 all the four new chains which were fastened, 

 in addition to the old anchor- chains, two to 

 the end of each cable. The new pit is beyond 

 the two old anchorages, at the back of the 

 old wall. The new anchor-chains connected 

 with the upper cables pass in long links in a 

 straight line from the point where they curve 

 down to the anchor-plate to the end of the 

 cables. The chains fastened to the lower ca- 

 bles pass from the same point, in still longer 

 links, on each side of the old anchor-chains of 

 the upper cable to the old lower cable anchor- 

 age, where they have to make an upward bend 

 to join the end of the cables. This is secured 

 by fastening the pins of the short links, which 

 succeed to the pins of the old anchor-chain, 

 by stirrups. The pits are 6 feet by 2 feet 6 

 inches. The anchor-plates are of cast-iron, 5 

 feet 6 inches square, and strongly ribbed. One 

 pin passes through the plate and the whole 

 eight links of the anchor-chains. The pits 

 were sunk 17 feet deep on the New York side 

 and 23 feet on the Canada side. The chamber 

 for the reception of the plate at the bottom of 

 the pits was 6 feet by 7. In filling up the pits 

 no stone was permitted to come in contact 

 with the chains. In renewing the iron-work 

 of the superstructure, it was decided to use 

 steel for the posts, chords, track-stringers, and 

 lateral rods, and to make all other parts of 

 iron. The new iron beams were first put in 

 nearly throughout. The portion of the new 

 work thus put in weighed 1,100 pounds per 

 running foot. There were 150 feet of the new 

 work finished at a time, which was equivalent, 

 in the middle portions of the bridge, where 

 the work was begun, to about 70 tons of ex- 

 tra dead load on the bridge. The weight of 

 the wooden portions of the old bridge was 

 estimated by John A. Roebling, at the time 

 of completion, at 1,000 tons. Added wood- 

 work and absorbed moisture are estimated to 



