MECHANICS AND USEFUL ARTS. 45 



bridge: Clear span, 1,600 feet; len,<Tth of brids^e between the 

 towers, 1,665 feet; total length, including approaches, 2,499 feet; 

 height of bridge above high water, 155 feec ; height of towers 

 above the water, 280 feet; working safe load for the railroad 

 lines, 2,400 tons ; working safe load for the highways, 2,880 tons; 

 total safe load for the bridge, 5,280 tons; load that would break 

 the bridge, 25,171 tons ; miles of steel wire in cables, 70,302 ; total 

 weight of iron and steel in the bridge, 17,005 tons ; total amount 

 of masonry, 58,084 cubic yards; total suspended weights, 9,651 

 tons. 



There will be 20 cables in 4 systems; each cable will be 14 

 inches in diameter. The bridge will carry at one time 32 passen- 

 ger-cars ; it would carry safely 34,560 people and 60 locomotives, 

 if they could be placed upon it at once ; 18,000 peojDle and 53 loco- 

 motives would fill it. From the dimensions given above, it will 

 be seen that this bridge will be longer than any one yet built on 

 the continent, though a span of 1,610 feet is projected in the 

 bridge undertaken to be built across the St. Lawrence at Quebec. 

 — Scientijic American. 



Franz Joseph Bridge at Prague. — This is built on the rigid sus- 

 pension principle of Mr. R. M. Ordish, of Westminster, England. 

 It was formally opened June 21, 1868. About a month before the 

 opening it was tested in the following manner : The foot-paths 

 were loaded with bricks, 80 pounds per superficial foot. While 

 this load was on, a double line of vehicles, each loaded with 4 tons 

 of old rails, was driven on to the bridge, remaining there for about 

 10 minutes. The total deflection obtained with the bricks and the 

 movins: load was H inches, the calculated deflection havinof been 

 8 inches. After moving the loads a permanent set of seven-eighths 

 of an inch was registered, the test giving entire satisfaction. The 

 bridge is 820 feet long between abutments, and 32 feet wide. The 

 total cost was £57,000. 



Railroad Bridge across the Mississippi. — On the 7th of I^ovem- 

 ber the formal opening of the Quincy (111.) Railroad Bridge across 

 the Mississippi River took place, making an unbroken railway 

 line from the East, via Chicago, to Kansas City on the Missouri. 

 When the bridge at this place shall be finished the through line 

 will penetrate the heart of Kansas. AVe coj)y from the " Chicago 

 Railway Review" the following description of the bridge : — 



♦' The first stone was laid Sept. 25, 1867, the last Aug. 5, 1868. 

 Its total length, including embankments, from the Chicago, Bur- 

 lington, and Quincy to the St. Joseph Railroad tracks, is about 2 

 miles. The draw portion of the bridge spanning the main chan- 

 nel of the river consists of 2 spans of 160 feet each ; and the main 

 bridge consists, otherwise, of 2 spans of 250 feet, 3 of 200, and 11 

 of 157 each, — making a total, with the mason work, of 3,250 feet. 

 The embankments and trestle-work between are 1,400 feet in 

 length ; Bay Bridge, 613 feet; 1 draw, 190 feet long; and 4 spans 

 of 85 feet each. The bridge is elevated 10 feet above high-water 

 mark, and 20 feet above low-water mark, on stone piers. The 

 masonry and foundations are the work of the Bridge Compan}% 

 under the direction of the Chief Engineer. The superstructure is 

 5 



