1854.] 



THE VICTORIA BRIDGE. 



291 



trains passing through it, and made of sufficient strength to carry- 

 six times the heaviest load hitherto known to travel on railways 

 in this or any other country." 



In the accompanying plate of the Victoria Bridge, the centre 

 arch is indicated by the steamer passing through it; the width 

 between the towers is here 330 feet, or 110 yards, and the 

 enormous tube which spans the gulf must be constructed so as . 

 " to sustain six times the heaviest load hitherto known to travel 

 upon any railway in the world." Of course this is to be under- 

 stood as applying to a train or part of a train 110 yards long — - 

 nevertheless involving a degree of strength and durability of 

 which it is extremely difficult to form a just and accurate con- 

 ception. 



We hope to be able to furnish diagrams and descriptions of 

 the details of this great Canadian work in future numbers of the 

 Journal. 



It will not be inappropriate, perhaps, to announce here the 

 intention of the Council of the Institute to publish, from time to 

 time, plans and views of the leading structures on the Grand 

 Trunk, the Great Western, and other railways of Canada. Nor 

 do. we think that the time is far distant when — in continuing our 

 illustrations of the great public works of this country — we may be 

 enabled to delineate the details of the unrivalled Welland and 

 St. Lawrence Canals, the Slides of the Ottawa, the Suspension 

 Bridge and Rideau Locks at Bytown and other magnificent 

 structures, which are scarcely known except by a misty reputa- 

 tion beyond the counties in which they are situated. 



Subjoined is Mr. Stephenson's report on the Victoria Bridge 

 to the Directors of the Grand Trunk Railway : — 



24, Great George Street, Westminster, 

 2nd May, 1854. 



Gentlemen, — -Absence from England, and other unexpected circum- 

 stances, have prevented my sooner laying before you the results of my 

 visit to Canada last autumn, for the purpose of conferring with your 

 Engineer-in-Chief, Mr. Alexander Ross, respecting the Victoria Bridge 

 across the River St. Lawrence, in the vicinity of Montreal. 



The subject wdl naturally render itself into three parts, viz. : — • 



First, — The description of Bridge best adapted for the situation. 



Second, — The selection of a proper site. 



Third, — The necessity for such a structure. 



Regarding the first point, I do not feel called upon to enter upon a discus- 

 sion of the different opinions which have been expressed by engineers, both 

 in England and America, as to the comparative merits of different classes 

 of bridges, and more especially as between the suspension and tubular 

 principles, when large spans become a matter of necessity. It is known to 

 me that in one case in the United States a common suspension bridge has 

 been applied to railway purposes, but from the information in my poses- 

 sion from a high engineering authority in that Country, the work alluded to 

 can scarcely be looked upon as a permanent, substantial, and safe structure. 

 Its flexibility, I was inlbnned, was truly alarming, and although another 

 structure of this kind is in process of construction near Niagara, in wdiich 

 great skill has been shewn in designing means for neutralising this tendency 

 to flexibility, I am of opinion that no system of trussing applicable to a 

 platform suspended from chains will prove either durable or efficient, unless 

 it be carried to such an extent as to approach in dimensions a tube tit itself 

 for the passage of railway trains through it. Such bridge may doubtless be 

 sucessfully, and perhaps with propriety, adopted in some situations, but I 

 am convinced that even in such situations, while they will in the first cost 

 fall little short of wrought iron tubes, they will be more expensive to main- 

 tain, and far inferior in efficiency and safety. 



I cannot hesitate, therefore, to reeoromend the adoption of a Tubular 

 Bridge, similar in all essential particulars to that of the Britannia over 

 the Menai Straits in this Country; and it must be observed, that, the essen- 

 tial features being the same, although the length much exceeds that of the 

 work alluded to, none of the formidable difficulties which surrounds its 

 erection will be involved in the present instance. In the Britannia, the two 

 larger openings were each 460 feet, whereas in the proposed Victoria there 



is only one large opening of 330 feet, all the rest beinoc 340 feetj In the 

 construction of the latter, there is also every facility for the erection of scaf- 

 folding which will admit of the tubes being constructed in their permanent 

 position, thus avoiding both the precarious and expensive process of floating, 

 and afterwards lifting the tubes to the final level by hydraulic pressure. 



In speaking of the facilities, it is a most agreeable and satisfactory duty 

 to put on record that the Government Engineering Department has, llnough- 

 out the consideration of this important question, exhibited the most friendly 

 spirit, and done everything in its power to remove several onerous con- 

 ditions which were at one time spoken of as necessary, before official 

 sanction would be given for the construction of the Work. 



On my arrival in Canada, I found that Mr. A. M. Ross had collected so 

 much information bearing on the subject of the site of the Bridge, that my 

 task was comparitavely an easy one. 



Amongst the inhabitants of Montreal, I found two opinions existing on 

 this point — somewhat conflicting: the one side maintaining that the River 

 should be crossed immediately on the lower side of the city, where the 

 principal channel is much narrower than elsewhere, and where also the 

 Island of St. Helens would shorten the length of the Bridge ; the other 

 seeming to be in favour of crossing a little below 7 Nun's Island. 



Sections of the bed of the River at both points had been prepared, and a 

 careful study of these left no doubt on my mind that the latter was deci- 

 dedly the one to be adopted/ 



In addition, however, to the simple question of the best site for the 

 construction of a bridge across the St. Lawrence, my attention was specially 

 called to the feasibility of erecting and maintaining such a structure during 

 the breaking up of the ice in spring, when results take place which appear to 

 every observer indicative of forces almost irresistible, and, therefore, such as 

 would be likely to destroy any piers built for the support of a bridge. I have 

 not myself had the advantage of witnessing these remarkable phenomena, but 

 have endeavoured to realise them hi my mind as far as practicable by conver- 

 sation with those to whom they are familiar, and, in addition to this, I have 

 read and studied with great pleasure an admirable and most graphic de- 

 scription by Mr. Logan of the whole of the varied conditions of the river, 

 from the commencement of tlie formation of ice to its breaking up and 

 clearing away in spring. To this memoir I am much indebted for a clear 

 comprehension of the formidable tumult that takes place at different times 

 amongst the huge masses of ice on the surface of the river, and w T hicb must 

 strike the eye as if irresistible forces were in operation, or such as, at all 

 events, would put all calculations at defiance. 



This is no doubt the first impression on the mind of the observer ; but 

 more mature reflection on the subject soon points out the source from which 

 all the forces displayed must originate. 



The origin of these powers is simply the gravity of the mass occupying 

 the surface of the water with a given declivity up to a point where the river 

 is again clear of ice, which in this case, is at the Lachine Falls. This is 

 unquestionably the maximum amount of force that can come into play; but 

 its effect is evidently greatly reduced — partly by the ice attaching itself to the 

 shores, and partly by its grounding upon the bed of the river. Such modi- 

 fications of the forces are clearly beyond the reach of calculation, as no 

 correct date can be obtained for then estimation ; but if we proceed by 

 omitting all consideration of those circumstances which tend to reduce the 

 greatest force that can be exerted, a sufficiently safe result is arrived at. 



In thus treating the subject of the forces that may be occasionally applied to 

 the piers of the proposed bridge, I am fully alive to many other circum- 

 stances which may occasionally combine in such a manner as apparently 

 to produce severe and extraordinary pressure at points on the mass of ice or 

 upon the shore, and, consequently, upon the individual piers of a bridge. 

 Many inquiries were made respecting this particular view, but no facts 

 were elicited indicative of forces existing at all approaching to that which 

 I have regarded as the source and the maximum of the pressure that can 

 at any tune come into operation affecting the bridge. 



I do not think it necessary to go into detail respecting the precise form 

 and construction of the piers, and shall merely state, that in forming the 

 design, care has been taken to bear in mind tire expedients which have 

 hitherto been used and found successful in protecting bridges exposed to the 

 severe tests of a Canadian winter, and the breaking of the ice of frozen 

 rivers. 



I now come to the last point, viz., the necessity of this large and costly 

 bridge. 



Before entering on the expenditure of £1,400,000 upon one work in any 

 system of Railways, it is of course necessary to consider the bearing which 

 it has upon the entire undertaking if carried out, and also the effect which 

 its postponement is likely to produce. 



