30 ANNUAL OF SCIENTIFIC DISCOVERY. 



. did timber bridges upon this principle. They possess, at the 

 present day, numerous gigantic examples of this method of con- 

 struction, embodying every principle, with the exception of that 

 of suspension, which could possibly he introduced in the erection 

 of timber spans. It must not be supposed that the form of 

 girder in question sprung into full development upon its first 

 appearance among us. Far from it. The earliest examples of 

 wrought-iron open-sided girders were erected in Ireland. We 

 may select, as a specimen of their original construction, a bridge 

 carrying the Dublin and Drogheda Railway over the Royal Canal 

 in Dublin. However worthy of commendation, as a pioneer of 

 the new principle, this bridge may be considered, it cannot be 

 otherwise regarded than as a miserably inefficient application of 

 it, or rather as no correct application whatever. The web, where- 

 in lies the especial value of the system, is composed of a series of 

 thin bars closely interwoven and riveted together, so closely as to 

 present a completely reticulated appearance, and without the 

 slightest attempt at proportion or distribution of material, and 

 constitutes a perfect mockery of all the laws laid down by theory 

 for correctly designing girders of this nature. Curiously enough. 



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about 30 miles further on, upon the same line of railway, we 

 have in the Boyne Viaduct one of the finest existing examples of 

 the lattice principle, where the laws of theory have been closely 

 adhered to, and only received that modification which must al- 

 ways accompany their practical application. Comparing these 

 two structures together, and contrasting the total absence of all 

 scientific principles and theoretical requirements in the one with 

 their full and accurate development and application in the other, 

 it is scarcely possible to believe that the two designs could have 

 emanated from the same individual. The Engineer. 



THE OHIO RIVER BRIDGE AT LOUISVILLE. 



This is a Fink truss bridge, of which a number are built at 

 different points on the Louisville and Nashville Railroad; the 

 largest is at Green River, and it has been admired by many dis- 

 tinguished architects and engineers of this country and of Europe. 

 It is the invention of Hon. Albert Fink, who will superintend the 

 construction of the Louisville Bridge. The entire length will be 

 3,650 feet, with a pivot bridge across the canal of 280 feet. The 

 location will be fixed somewhere between the Elm Tree Garden 

 and Rock Island. It will be reached by a grade of about 70 feet 

 to the mile on each side of the distance for nearly 350 yards. 

 There will be 13 spans of 250 feet each, with one large span of 

 400 feet across the Indiana chute. The bridge will have an ele- 

 vation of 90 feet above low water and 49 feet above the high 

 water of 1832. The superstructure, which is entirely of iron, 

 will be 152 feet above the foundation, while the floor of the bridge 

 is elevated at 120 feet above the. foundation. It will require 

 a-bout 756,000 cubic feet of stone ; but the cost of the entire bridge 

 will be at least one-fifth less than that of any other which would 

 answer the same purpose. The suspension bridge at Cincinnati 



