330 Transactions of the American Institute. 



ways to traverse rivers or ravines by means of these bridges, instead 

 of the costly viaducts or heavy embankments; and Mr. Rendel saw 

 no difficulty in giving any required amount of rigidity to the plat- 

 forms; it was only necessary to increase the strength of the framing 

 to enable tLe roadway to bear with perfect safety the passage of 

 an engine and train of carriages. 



In the meantime the wire bridges found a favorable reception 

 in France, which is full of admirable structures of this kind, and 

 the French engineers brought the manner of constructing cables to 

 the high degree of perfection of our day. 



After the preceding introduction of wire bridges in England and 

 Switzerland, the brothers Seguin constructed the first wire suspen- 

 sion bridge in France, in the year 1824. All the existing methods 

 of splicing wire, of bringing up the cables, have been studied, and 

 theories of great mechanical value have been invented. 



The cables were first made on land and then carried on the 

 towers by machinery, but soon the French engineers began to 

 build them on the towers themselves. Very perfect methods 

 have been employed, securing all possible equality of tension in 

 the single wires; and as greater perfection always requires more 

 time and trouble, these methods are more expensive than those of 

 a later origin, which, shortening a little the time of construction, 

 are not securing the same equality throughout. 



Now, the time to make a wire cable of one thousand six himdred 

 feet length, is about one year, which involves a great loss when we 

 consider that steel chains can be obtained cheaper, much more 

 secure, much lighter and better than any wire rope can be, and by 

 the use of which the time for building suspension bridges is con- 

 siderably reduced. 



Such a steel chain bridge was built in Vienna in the year 1829, 

 by the Austrian engineer, Mitis. It is praised in all reports as a 

 strong structure. 



The wrappings of the French cables are made at intervals of 

 about one foot; in later times the wrappings have been made 

 continuous. 



i 



In the year 1831, the French engineer Vicat, in his report on 

 the suspension bridges across the river Rhone, described his method 

 for building wire bridges in place, directly on the towers and abut- 

 ments, a method which, essentially in the same manner was copied 

 by erecting the Niagara and Cincinnati bridges. This method is 

 described as follows: 



