546 APPENDIX. 



The accident happened through the vibration 

 caused in the structure, by the marching of a 

 troop of Soldiers over it. They were four 

 a-breast, and about 60 of them on the bridge, 

 the foremost being half way across, when they 

 heard a tremendous crash hke a continuous 

 discharge of musketry, and in a moment one 

 side of the bridge sunk down, sloping into the 

 river, dragging after it the main pillar, which 

 they had passed on their right, with the 

 stone to which it was attached, and throwing 

 every one upon the bridge into the river or 

 among the chains. Some of the men escaped 

 unhurt, several were injured, but fortunately 

 no lives were lost. 



Immediately after the accident I went down, 

 at the request of the parties connected with the 

 bridge, to ascertain the cause of the failure. 

 I found that the principal fracture had taken 

 place in the main chain, near to its termination 

 under ground, and where it appeared there 

 was an error in its construction, which ren- 

 dered it much weaker than any where else, 

 though being under ground the defect was not 

 previously visible. 



The chain, which has been partially described 

 in page 385, is of malleable iron, and is 



