This is a subject which, next to the effect of high winds, is most important to be considered. The Niagara Bridge is a great thoroughfare for all kinds of stock. Droves of cattle are, according to the regulations, to be divided off in troops of twenty, no more than three such bodies, or sixty in all, to be allowed on the bridge at one time. Each troop is to be led by one person, who is to check their progress in case they should start off on a trot. If these rules and regulations are strictly observed the bridge will be spared much abuse. On several occasions I have noticed the injurious effect produced by twenty heavy cattle under a full trot. Standing on the lower floor at the time I could perceive no apparent motion in the bridge, but felt a most intense trembling and short vibration. If the cattle happen to move all on one side, outside of the centre, the effect produced is also lateral, and consequently severe- upon the framing. The great inherent stability of the structure will so far resist this action as to prevent all such motions as would be readily discovered by the eye. But I will state here that in my opinion a heavy train, running at a speed of twenty miles an hour, does less injury to the structure than is caused by twenty heavy cattle under a full trot. Public processions, marching to the sound of music, or bodies of soldiers keeping regular step will produce a still more injurious effect. No bridge, constructed without regard to stability, will long resist such tests. The best built suspension bridge, as well as all kinds of wooden or iron structures, not excepting tubular bridges, will suffer from this cause. The Covington Suspension Bridge opposite Cincinnati, with a single span of 550 feet, erected last year, and since rebuilt, fell down under twenty cattle trotting over.

The above remarks have been made with a view to correct popular notions upon this subject, and also to draw attention towards it, so that the superintendent of the bridge may be directed to see the rules and regulations already laid down strictly enforced,

In conclusion I will state that the woodwork was entrusted to the charge of Mr. D. McKenzie, as master carpenter, who last year sustained a serious injury while removing the old wooden towers on the Canada side, and has been since assisted by Mr. L. Anson. The wire work and other parts have been attended to by Mr. David Rhule. During the first two seasons I was assisted by W. O. Buchanan, Esq., and latterly by J. H. Fisher, Esq., who is also acting in the capacity of Secretary to the Joint Board To all these gentlemen I wish to express my obligations for their cordial and efficient co-operation in the execution of the works.

In this memoir, and reporting on the final and successful completion of the bridge, I should be doing injustice to my own feelings as a man if I did not avail myself of this opportunity to thank the President and Directors of the Niagara Falls Suspension and Niagara Falls International Bridges Companies for the unwavering confidence which they have always placed in my professional ability. When engineers of acknowledged talent and reputation freely expressed their doubts as to the success of this work, a wavering of confidence on their part would have been but natural But I am happy to state here that in all my operations I have always met with a cordial support. It is a great satisfaction that this work has turned out equal to the promise made, and also to acknowledge the mutual confidence that has existed.