Polytechnic Association Proceedings. 823 



But the English engineers were the first who proposed and 

 applied stays for suspension bridges, in connection with cables 

 as well as without them. 



The first of these bridges was built by Richard Lees, at Galashiel, 

 across the river Gala, in the year 1816, of a span of one hundred 

 and twelve feet; it was like the two following, a wire bridge. The 

 bridge at King's meadow, across the Tweed [span one hundi-ed 

 and ten feet], was built in the year 1817, and another structure at 

 Thirlstone Castle, one hundred and twenty-five feet long — both with 

 stays. At Kelso, on the Tweed, a bridge of three hundred feet 

 span was built for carriages — the roadway eighteen feet in width. 

 A bridge at Dryburgh Abbey, with stays, was two hundred and 

 sixty feet long, and very movable; so much so, that four persons 

 could shake it so as to break one of the stays. In the year 1818, 

 a wind destroyed the whole structure. Rebuilt according" to 

 Finley's system, provided with strong longitudinal beams, strong 

 railings and anchors like those at Niagara bridge, it resisted the ob- 

 noxious motion. Especially is it stated that the railing resisted all 

 upward movements. The use of anchor chains, to prevent side 

 and upward movements of the floor is, therefore, already very old, 

 and Sir Samuel Brown often made use of them. 



The bridge at Dryburgh is very interesting in another reference, 

 as it is the first wherein the chains were convergent in the middle of 

 the span. At the towers of this bridge the distance apart of the 

 cables was twelve feet, and in the middle of the bridge it was only 

 four feet; the object being to reduce the side motion. But the engi- 

 neer, Stevenson, already observed that he preferred to keep the 

 parallelism of chains, and rightly, as I hope fully to convince you 

 in a future communication. 



A great many of the stay bridges broke down, and after many 

 sad experiences, the use of stays has been entirely rejected by 

 English engineers, notwithstanding they have been reintroduced 

 into this country. 



Navier saw difierent bridges built by Brown in England, and he 

 describes the action of the stays in aiding to support the floor; 

 others were introduced horizontally, but inclined to the longitu- 

 dinal axis of the bridge, to reduce the side motion, and he criti- 

 cised sharply the combination of stays with suspension rods and 

 chains or cables. 



The use of separate tension cables attached to the two towers, 

 •working horizontally or vertically against the action of the wind; 



