ItioS] 



RAILWAY BRIDGE OVER THE ST. LAWRENCE. 



T7 



of which is across the general direction of the stream, and strikes 

 toward the quays at Montreal. 



Considering the " channel " as that portion of the stream having a 

 greater depth than nine feet at extreme low -water, the width uf it on 

 the bridge line as stated is about 360 fee' rr about 300 feet between 

 the lines of ten feet water. If the cent . be executed in wood, 



the piers would encroach upon the " chai,. . --' as above defined. It 

 would be belter to have tbo centre span upon aoy location 400 feet 

 wide, which will involve a tubular beam of iron, at an additional ex- 

 pense of about £43,000. This additional expenditure I would recom- 

 mend, as this arch will be exposed 'o the chimneysof passing steamers; 

 moreover, by making it of iron it cuts off the communication in the 

 eveut of fire — exposing only half the structure. 



While the selection of the site has been governed by the accidental 

 conditions of the river, it possesses a variety of advantages, which 

 under such circumstances could hardly have been anticipated. 



1st. The location is on the most direct line of connection for the 

 Grand Trunk Railway. This road, without reference to the bridge, 

 ■would on approaching the city cross the canal at the only convenient 

 point (which is near Gregoiy's and above all the basins) aid proceed- 

 ed down to Poiut S'. Charles for its freight terminus and for a connec- 

 tion with the harbour independent of the canal. The biidge line is a 

 Continuation of the main track coming down to Point St. Charles. 



2nd. The lino in the river runs upon a rock bottom and in more 

 shallow water than can be found upon any other direct line crossing 

 the St. Lawrence. It is a remarkable fact that the shoalest water to 

 be found in the St. Lawrence below Lake Ontario is on the last rapid 

 ■ — the Sault Normand opposite Montreal. 



The width of the river and consequent length of the bridge is not 

 only counteracted by this shoal water (fully half of Ihe whole diatunce 

 being less than five feet deep,) hut this width involves little di-advan- 

 tage, because the distance between the only navigable channel and 

 the shores admits of a gradient, which passingovcr the limits required 

 for the navig lion, yet descends at once so as to strike the business 

 level at both of these shores. 



3rd. The ice seldom lodges above the line of the bridge, although it 

 alwayB does to a greater or less degree immediately below it. Nun's 

 Inland gives a direction to the current, which throws the ice against 

 Moffatt's Island whers it piles with great force. The shoal, which is 

 suspended from the lower end of Nuns' Island to the ceEtie channel 

 will act aa a breakwater to the western half of the bridge against the 

 effect of " bergs" of ice. The average depth of water on this shoal 

 not exceeding seven feet, detached ice-breakers can be constructed 

 upon it at a moderate c> st, which will break the momentum of large 

 descending fields, — while accumulations of ice having too great a 

 draught of water to pass under the arches will be "picked up" by 

 this shoal before reaching the piers of the bridge. On the eastern half 

 of the bridge, the greater portion of the work will derive much protec 

 tior against the effects of descending ice, by the works of the Cham- 

 plain and St. Lawrence Railway, and by the natural breastwork of 

 Moffat's Island. 



4th. The site, while it possesses all the advantages of a line in the 

 rapids where there is but one navigable channel, not only has that 

 channel narrower than any available one in the rapids above, but the 

 rapid is so moderate as not to offer any great impediment to the work 

 of erection, and construction, and for three months in the year is 

 frozen over and accessible at every poiut upon strong ice. 



5th. Terminating at Point Charles in immediate contiguity with 

 the canal basins, the water level of which aided if necessary by an ad- 

 ditional supply from the head of the Lachine rapids can be conducted 

 over hundreds of acres both on land and in the river, — the bridge will 

 lead all the railroads from the southern shore to the only point where 

 they can be placed in immediate connection with the navigation and 

 receive supplies " ex-warehouse," or direct from iuland or sea craft for 

 distribution to every part of New England or the Lower Provinces. 

 In connection with this subject I have projected a scheme of docks 

 around Poiut St. Charles, which shews the capabilities of the place in 

 point of extent to be at least equal to that of Liverpool, Glasgow, or 

 London, and which may be taken up in sections and extended as re- 

 quired for the increasing wauts of commerce. 



The importance of this point, its fitness for a general railway termi- 

 nus in connection with the sea and inland navigation, is explained at 

 large in the appendix in an extract from my unpublished Report on 

 the Montreal and Kingston Railway, and also an extract from a lecture 

 before the Mechanics Institute of this city. 



It will be at once seen on reference to a map, that the whole of the 

 channel between Nuus' and Montreal Islands may be filled with water 

 and made available for the navigation. Also by obtaining (upon top 



of the embankment) permanent access to Nuns' Island, the outer coast 

 of that island presents an extensive frontage and deep water where 

 barges and lake and river craft not drawing over nine feet water may 

 load for ports below. 



It is only by aa artificial harbor accommodation like this that Mon- 

 treal can ever hope to share with Quebec any portion of the export 

 trade in deals. Bright deals brought by railway to Point St. Charles 

 aud Nuns' Island, could afford this transportation on account of the 

 higher price these command over those which have been floated. This 

 trade by attracting a larger marine to this port could not fail to give 

 an important impulse to our commerce, 



Lastly. The excellence of this site, — opposing only a single navi- 

 gable channel which is trumpet-'mouthed and therefore affords safe 

 and easy access to the passage of the bridge, — is strikingly shown iu 

 the features of practicability, of economical arrangement, and the 

 minimum of gradient which are here attainable. 



If the navigable channel were a quarter of a mile or more in width, 

 as it is both above and below the proposed line of the bridge, it would 

 be necessary to elevate all that portion of the bridge which spanned 

 this chanuel. one hundred feet. This would shorten the distance iu 

 which the ascent from the shore to the highest point of the bridge 

 must be made, so as either to increase the gradient to an impractica- 

 ble figure or augment the cost and length of the bridge. The increased 

 cost might make it commercially impracticable, and the increased 

 length might throw the terminus on shore at a poiut which would 

 greatly damage if not dastroy its commercial usefulness. Again, if 

 there were several navigable bays under the bridge these would be 

 separated by piers splitting the current, so as to make the navigation 

 dangerous. 



The economical arrangement consists in the fact that it will only be 

 necessary to elevate the two p".ers embracing the channel to the height 

 of one hundred feet above the water ; over these a rectangular tubular 

 beam (30 feet deep, and assisted by arches, if of wood, but without 

 arches and of less depth if of iron) will be laid — through which the 

 trains will run The piers immediately on either side of these central 

 ones will only be raised seventy feet above the water, and from these 

 toward either shore the height of the piers will gradually dimmish, iu 

 proportion to the gradient of the bridge- The trains will run vpon the 

 top of the bridge in ascending from either shore to the centre arch, 

 and the depth of the lubes (thirty feet) will, without additional cost, 

 make up so much of the required elevation of the track, and thus be a 

 substitute for a corresponding amount of masonry in the piers. This 

 dropping! of the bridge immediately on either side of the centre span 

 is here admissable — because no masted craft will pass under the side 

 arches — but would obviously be iuadinissable if the navigable chan- 

 nel extended over a greater portion of the river. 



The comparative lightness of the gradient is due to the existence of 

 of the single narrow channel and its position nearly in the centre of 

 the bridge line, from the combined effects of which the greatest possi- 

 ble distance is obtained for surmounting the level between the shores 

 and summit of the bridge. 



PRINCIPLES OF CONSTEUCTIOX. 



In the foregoing part of this report, the plan of the proposed bridge 

 has been partly developed, but iu consequence of its relalion to the ac- 

 tion of the ice, its peculiar position and arrangement, it will be neces- 

 sary to allude to it more fully. 



The importance of retaining the "bordage" ice in situ has been ex- 

 plained, and for this purpose, that part of the bridge extending from 

 the shores over the shoals, to the depth of five feet water, being a dis- 

 tance of 450 yards on one side, aud 570 on the other, is designed to be 

 a solid causeway or embankment carried above the level of the high- 

 est winter flood ; from which poiut to the level of the rails it may be 

 carried up by a viaduct of arches — an embankment or trestle work for 

 the present. If the scheme of docks which I have proposed at Poiut 

 St. Charles, be carried out. this causeway would become one of the 

 dock walls, and the arches erected on it to give the proposed ascent 

 to the biidge might be converted iuto warehouses. If the chaunel be- 

 tween Nun's Island and Point St. Charles be dammed, an immense 

 amount of ice which now goes down to aid in flooding the water back 

 on Montreal, would be retained harmless until it melted in the 

 sprin.g 



On the south-eastern shore the great width and dead shoal water 

 around tha Laprairie basin, form square miles of ice, which, so soon 

 as freed from its attachment to the shore, is carried by the throw of 

 the current directly down through the now important chanuel between 

 Moffatt's Island and the St. Lembert side. The works of the Cham- 

 plain and St. Lawrence Railroad Company, althongh incomplete and 

 not high enough, retained this bordage in situ during last winter, (1851 

 — 1852) and this in connection with the fact that the winter set in 



