Suspension Bridges and other Structures, 393 



use to adopt the various methods of staying that have hitherto 

 been adopted ; it is of no use to carry a stay-chain to the mid- 

 dle of the roadway,fig. 12, nor even four stays as at 2, 3, and 4, 



Fig. 12. 



because it will vibrate exactly as at figs. 9 and 11, neither would 

 stays at 2 and 3, as in fig. 13, produce the effect, because the 



Fig. 13. 



bridge would still oscillate as in fig. 10. 



Mr Brunei has proposed a method of preventing oscillation, 

 which, though ingenious, is expensive and heavy, and yet has 

 not the desired effect. He has proposed an inverted chain 

 below the bridge ; but, besides the disadvantages of great ex- 

 pense and weight, this still leaves the cause of oscillation un- 

 removed, for the whole will, in the manner already described, 

 perform isochronous oscillations. 



It is obvious, therefore, that, unless the cause of the propa- 

 gation of continued and equal-timed oscillations throughout the 

 I structure be thoroughly understood and prevented, additional 

 weight or strength given to the parts, will merely have the ef- 

 fect of uselessly loading and weakening the whole. 

 The following is the plan on which alone the oscillations are 

 to be reduced to the smallest possible extent in the most cffec- 

 VOL. XXVI. NO. Lll. APRIL 1839. 

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c c 



