Mechanical Science. 369 



Other experiments were made with reference to the effect of tempe- 

 rature on the tenacity of the wire, but for results of this kind, we refer 

 our readers to p. 373, vol. x v. , of this Journal : the results there stated 

 are the same as those quoted with the above. — Bib. Univ. xxiii. 305. 



2. Suspension Bridge of Iro.% Wire at Geneva. — The preceding 

 researches have been applied with the greatest success, in the con- 

 struction of two bridges across the dry ditches of the fortifications of 

 Geneva. The first of these ditches is 33 feet deep and 10S feet 

 wide at the site of the bridge ; the second is 22 feet deep and 77 feet 

 wide ; they are separated by what is called the countergard, which is 

 about 70 feet wide, and the top of which is level with the surround- 

 ing soil. A stone building is erected on the city edge of the first 

 ditch, which serves as a point of attachment for the wires, as a gate to 

 the city, and also as a station for the persons who have charge of the 

 bridge ; a piece of masonry is erected on the countergard, as a point 

 of support for both bridges ; and a third erection of a similar kind, 

 serves as an outer gate, and for a support to the end of the outer 

 bridge. The wire used is of the kind called No. 14 in commerce, 

 very nearly of the diameter of the second sort referred to in the pre- 

 ceding experiments ; it is made up into lengths or bundles, each 

 containing 100 wires, and there are three such collections on 

 each side of the bridge. As the line of suspension proceeds uninter- 

 ruptedly across both ditches and the intervening bank, the length was 

 found too great for one bundle; they were therefore made in 

 shorter lengths, terminating at each end with a ring, and were con- 

 nected by placing these rings side by side, and passing a strong iron 

 bolt through them. Each single wire was first stretched by a weight 

 of 220lbs., then made up into the bundles of 100 each, which were 

 united by iron ties at successive intervals, and the whole rolled round 

 with iron wire, which gives to them the appearance of cords. The. 

 longest of these bundles are 120 feet each, the others were made 

 shorter, as being more convenient for the situation they would 

 occupy in the line of suspension. From this arrangement it is evident 

 that each of the six main lines of suspension may be considered as one 

 bundle, though consisting of many parts; they are made fast atone 

 extremity to a plate of iron (irmly attached to the stone gate before 

 mentioned, then pass over the first ditch, across the stone support on 

 the countergard, over the second ditch, over the second standard, and 

 are dually made last to iron bars, which being attached to plates, are 

 loaded with masses of stone and buried in the earth. 



From the six principal lines other lines descend consisting each of 

 twelve wins only ; these arc made fast to the traverses, or pieces of 

 wood which form the bases of the bridges. On these are mortised long 

 pieces of carpentry, which are bolted together with them, and to which 

 are fastened the railings of the bridges, and then other planks are 

 fastened across these again, forming the path of the bridge. 



The rapid and complete success of this undertaking, does great 



Vol XVI. 2 B 



