REVIEWS — REPORT ON VICTORIA BRIDGE. 475 



tension in the bottom, — the only saving that can by any possibility be made to 

 take place being confined to the sides, must be a saving in that portion of the 

 weight which is only about 34 per cent, of the whole. How, therefore, can 70 

 per cent, of saving be realized, as has been stated, out of the total weight, when 

 the question resolves itself iuto a difference of opinion on a portion which is only 

 34 per cent, of such weight ? 



I am tempted to reiterate here much that was said by several experienced En- 

 gineers on the subject, during the discussions already alluded to, at the Institution 

 of Civil Engineers ; but the argument adduced on that occasion could only be 

 rendered thoroughly intelligible by the assistance of diagrams of some complexity, 

 and I think sufficient has been said to demonstrate that no saving of importance 

 can be made in the construction of the roadway of the Victoria Bridge, as it 18 

 now designed by the substitution of any other description of girder. Yet, lest 

 this should be considered mere assertion, permit me to adduce one or two exam- 

 ples, where the close-sided tubular system, and the open-sided system, may be 

 fairly brought into comparison with each other in actual practice. 



The most remarkable parallel case which occurs to me is the comparison of the 

 Victoria tubes under consideration, with a triangular or ' Warren' bridge, which 

 has been erected by Mr. Joseph Cubitt over a branch of the river Trent, near 

 Newark, on the Great Northern Kailway. 



The spans are very similar and so are the depths. In calling your attention 

 to the comparison, you must bear in mind that all possible skill and science were 

 brought to bear upon every portion of the details of the Newark Dyke Bridge, in 

 order to reduce the total weight and cost to a minimum. 



The comparison stands thus : 



VICTORIA BRIDGE AS BEING ERECTED. 



Span, 242 feet; weight, including bearings, 275 tons, for a length of 257 feet. 



NEWARK DYKE BRIDGE AS ERECTED. 



Span, 240 feet 6 inches; weight, including bearings, 292 tons, for a length of 



254 feet, 

 which shews a balance of 17 tons in favor of the Victoria tubes. 



The Newark Dyke Bridge is only 13 feet wide, while the Victoria tube is 16 

 feet, having a wider guage railway passing through it. 



This is a very important case, as the spans and depths are all but identical, and 

 it will therefore enable you to form a judgment upon that point which has caused 

 so much controversy at the discussion alluded to. It is true that in the Newark 

 Dyke Bridge a large proportion of the weight is of east iron, a material I have 

 frequently adopted in the parts of tubular bridges subjected to compression only, 

 but from its brittle character I should never recommend it for exportation, nor 

 for the parts of a structure that are liable to a lateral blow. 



It has been suggested that there is much convenience in the arrangement of 

 the trellis, or 'Warren' bridge, as it may be taken to pieces, and more conveni- 

 ently and economically transported overland than 'boiler plates;' this may be 

 correct under some circumstances, but it cannot hold good for a work like the 

 Victoria Bridge over the St. Lawrence. 



****** ******* 



Another example may be mentioned of a tubular beam, somewhat similar in 

 dimensions to the last described, and cue which is actually erected on a continua- 

 tion of the same line of railway, as that on which the Newark-Dyke Bridge is situa- 



