36 ANNUAL OP SCIENTIFIC DISCOVERY. 



Britannia, or Menai bridge. The whole will be made of wrought iron, and 

 will combine the principles of the suspension with those of the tubular 

 bridges. Including the viaduct, the bridge is 623 feet in length ; the 

 span or suspended part being 290 feet. There are two separate road- 

 ways, each being perfectly independent of the other, and their height 

 is 70 feet over the river Wye at high water mark, so that vessels can 

 pass under. The roadways of the bridge are formed of iron, put together 

 in plates, and in form they are similar to the tubes forming the Conway 

 and Britannia tubular bridges ; but, instead of being roofed in with 

 cellular divisions of iron, there is for each roadway, and suspended above 

 it, and at some distance, a strong cylinder of iron. It is suspended on 

 piers, and from the extremities of this cylinder a looped chain runs 

 under pins placed on each side of the roadway, in order to brace and 

 support it. Likewise strong iron braces pass from the cylinder to each 

 side of the tube, and from the top of each of these side supports to the 

 bottom of the other, chains are placed for additional strength. On one 

 side, the roadways rest on six upright iron cylinders, which have been 

 filled with concrete, and driven firmly on a foundation of rock. The 

 roadways on this side are continued in the form of a viaduct for about 

 three hundred feet more, resting upon these upright cylinders filled 

 with concrete, and firmly imbedded. On the other side, the roadways 

 rest upon solid rock. London Times. 



THE WHEELING SUSPENSION BRIDGE. 



EX-CHANCELLOR WALWORTH, who was appointed by the U. S. Supreme 

 Court a Commissioner to take testimony in the Wheeling Bridge case, 

 on the issue whether the bridge did or did not obstruct the navigation 

 of the river, has recently made a report on the subject, from which, 

 with the account published by Mr. Elliot, the engineer, it appears that 

 the length of the bridge, from centre to centre of the supporting towers 

 at each end is 1,010 feet, and the height of the flooring at its greatest 

 elevation, is 97 feet above the low water surface of the river. The 

 highest freshet ever known on the river at this point was in 1832, when 

 it rose 44 feet above its lowest level. There is, therefore, sufficient 

 height to permit a steamboat, with a pipe fifty feet above the water, to 

 pass under the bridge at the top of the flood of 1832. The testimony 

 taken by the commissioner, however, shows an increase in the height 

 of the chimneys of steamboats to 84 feet in some instances. The pas- 

 sage-way of the suspension bridge is 62 feet above the water zero on 

 Wheeling bar ; the highest chimneys would, therefore, strike when the 

 water was above 8 feet. It appears, from observations made at Wheel- 

 ing, that the Ohio is in good navigable order more than two thirds of 

 the year, and that it is the extreme of high and low water only five 

 days in the year. It being evident that the chimneys must be lowered 

 or the bridge elevated, and as the speed of steamboats is a great public 

 convenience, Mr. Wai worth pronounces in favor of the latter course. 

 The bridge must, therefore, be elevated "twenty-eight feet above the 

 highest point of the present bridge, and sixty feet above the elevation of 

 the bridge at the water abutment, on the eastern side." The estimated 

 cost of this elevation is $208,000. 



