Polytechnic Association Proceedings. 33 [ 



" The towers and abutments of a suspension bridge being finished, 

 the points of attachment ready to receive the cables, and supposed 

 that a number of double wires of equal lengths, forming circuits, are 

 wound on difierent reels, these wires are drawn from one pillar to 

 the other by means of a thin endless rope, like the guide rope of a 

 flj'ing ferry and moved like the chains of a chain-pump." 



By this method, Mr. Vicat proposed to make and suspend cables, 

 with less cost, with fewer workmen, and in shorter time than 

 before. He said it was not difiicult to reduce the number of cables 

 to two, if it was desired, whereby the surface exposed to oxidation 

 would be diminished; the tension of the single wires would be 

 uniform, whatever the thickness of the cables; the apparatus for 

 elevating the cables be simplified, and the greatest possible spans 

 would be admissible. 



More details on this subject can be found in the article on the 

 bridges across the river Rhone, in the French "Annales des Pouts 

 et Chaussecs," 1831, volume first. 



Mr. Chaley, the engineer of the celebrated suspension bridges at 

 Friburgh, in Switzerland, worked out Mr. Vicat's method, and 

 often had occasion to apply to it. He, according to the same 

 method, built the second suspension bridge at Friburgh, in Switzer- 

 land; further, the bridge " de la Charit6," across the river Laire, a 

 suspension bridge in Paris, another at Percey, in the Jura moun- 

 tains, and the bridges at Cormery, across the Indre, and of Beau- 

 mont, across the Sartlie, in France. 



Vicat's method was further employed at a bridge at Tours, in 

 France, for transporting materials. Interesting details are found 

 in the "Anuales des Ponts et Chaussees," in the year 1841. 



Other methods for constructing the cables of suspension bridges 

 directly on the towers and abutments, is that of the French engi- 

 neer Le Blanc, constructor of the splendid bridge at Koche-Ber- 

 nard; aud, after him, that method introduced by the French 

 engineer La Clerc, the constructor of the suspension bridge at 

 Lorient, across the Scorff. The anchorage of these bridges (the 

 .fiii'st is of 643 feet span, the other 610 feet) is interesting, as the 

 cables form one continuous belt, laid around the abutments in suit- 

 able vaults, allowing free circulation of the air, as well as to repair 

 the painting of the wire from time to time. The two cables, at 

 both sides of these bridges, have the same deflections, an arrange- 

 ment which is not objectionable. [The descriptions can be found 

 in the "Annales des Ponts et Chaussees," 1850.J 



