Dundee Advertiser, Tuesday 4 January 1870
(Letter written Dec 28 1869, published Jan 4 1870)
In a long letter, Matthew reviews once again the many reasons why the proposed Tay Bridge scheme at Dundee is ill-advised. The chances of accident are increased by the length and height of the bridge; by the planned bend in the bridge inducing structural stresses whenever a heavy train crossed it; by the thermal expansion and contraction inherent to an iron bridge; by the difficulty in detecting cracks and imperfections in iron compared to wood; by the increased chances of a damaging lighting strike to a high iron structure; and by the varied geology at Dundee making it likely that some bridge piers would be on solid foundations and others not.
In a memorable passage, Matthew imagines the scene of carnage that would follow a catastrophic collapse of the bridge while a heavy passenger train was passing over it, and the grisly feast that would be enjoyed by the Tay’s population of eels.
Matthew predicts economic ruin for the bridge, either in the wake of such a disaster or due to the lengthy and continual repairs that would have to be performed on the bridge to prevent it, or due to passengers being unwilling to be conveyed on so high and spindly a bridge. He points out that even great engineers like Brunel and Stephenson were capable of great blunders. He also points out that in wartime it would be an easy target for demolition by the enemy.
He ends by arguing for a low bridge at Newburgh, and how advantageous this would be in comparison to the current proposed scheme.
Unfortunately, the British Newpaper Archive is missing all issues of the Dundee Advertiser for 1870. The text below has been reproduced from “Evolutionary concepts in the Nineteenth Century: Natural Selection and Patrick Matthew” (Dempster 1996).
SIR,— Have the partisans of the proposed Dundee Bridge employed much thought upon the subject? They seem to have been so dazzled with the magnitude of the undertaking as to be blind to the difficulties next to insuperable. They certainly have not weighed the chances against its success with those for it — at least to me adverse chances far predominate. Its supporters seem not to be aware that in the case of such a bridge of more than a hundred spans the chance of accident is increased more than a hundred times. They now speak of fewer spans; this does not add to the security.
Here the chance of accident is also greatly increased by the height of the piers, and especially so when the bridge is crooked, and exposed to the impetus of a heavy, rapidly-rushing train, which acts with centrifugal force to throw the bridge outward from the centre of the curve. Besides, when the bridge is of long spans, and of iron, the long girders are subject to considerable expansion and contraction with every rise and fall of the thermometer — thus always in motion, creeping backward and forward upon the pier tops. The bridge is thus to some extent defective of adhesion, and the stability of each span mainly dependent upon its own weight pressure; or, if the girders are coupled together, the whole crooked bridge would be liable to an eel-like motion. The vibration given by the rapid motion of the heavy train (several hundred tons), with the creeping motion of the long girders, at such a height, and more especially if the foundation was not very secure, would in the course of a little time loosen the adhesion of the stones composing the piers, rendering the piers unsafe — that is, if they are not sooner thrown from the perpendicular and upset by the long lever power which their great length affords to a centrifugal force exerted at the top, to twist or sway them aside. Where there is a curve this force will be strongly exerted by a heavy rapid train. Were it not rapid, it would be behind the boat in speed, and useless. The boat passage must therefore be kept distinct from the North British Railway Company to prevent monopoly — that is, in the case of an improbable success in being erected and approved by inspectors.
There is another danger to which this enormous long and high bridge is exposed. Being chiefly an iron structure, there is a difficulty — an impossibility — of knowing the strength of an iron beam or tie as you can that of a beam of timber. Iron is also of different strength at different temperatures. Cracks, and inequalities of crystallisation and extension of crystallisation in cast iron, and what is termed brunt, burned, in malleable iron, are often imperceptible by the eye, and cannot be tested. In an extent of bridge such as this, about three miles, where hundreds of beams are employed, and where a defect in one may ruin the whole, destructive accident is highly probable. Besides, lightning in a thunder storm, attracted by the great height and length of an iron bridge, may do serious damage, may even injure a particular beam upon which the whole depends, although the injury be imperceptible.
The locality of Dundee presents much volcanic and earthquake disturbance. Bluets of lava here, forming projecting basalt rocks; deep depressions there, filled with sedimentary and volcanic mind, and various kinds of drift — instance the Meadows and the adjacent basalt rocks. We may expect similar inequalities in what is under water. The foundations of the piers will, we may expect, be very unequal, very unsafe, or very costly; some of them standing firm as the rock itself, others as false as the foundation of the Royal Exchange. At Newburgh, the red sandstone, at no great depth, affords a superior foundation.
Should the Bridge Company have to keep the bridge in repairs, the great amount of repairs which such a length and height of bridge would in all probability require, would go far to consume its revenue, while the charge of the Railway Company for stoppages which the repairs at times would cause, would be made to balance as far as possible the revenue they agreed to pay the Bridge Company. In the case of accident with a heavy passenger train (most likely with a heavy), the whole passengers would be killed or drowned. A few years ago a passenger train in France fell through a bridge into the water below, where only one man escaped, who dived through a carriage window. In the case of the Dundee Bridge, where from such a length and height liability to accident is so great, the highly possible accident of a drowned train would damn the Bridge for ever, and subject the Bridge Company to enormous damages, besides the lost principal. Nothing could exceed the horror of an islet in the Firth formed of iron, stones, and wood fragments, and of mangled human bodies, amongst which eels peered out, collected from all parts of the Firth by the carrion smell of which they are so very sensible. The eels (water-serpents), according to our Christian creed, might every one of them be demon possessed, come to gloat over in delight the horrible wreck and banquet. What more likely than an accident? Would the share holders persist in repairing the Bridge preparatory to another demoniac feast? Or would the Government, in tender regard for the life of Her Majesty’s subjects, not give order for the Company to remove the whole of the unhallowed fabric? At what cost would this be effected? Or would the North British not keep them to their bond?
The blunder of Brunel with the Great Eastern in constructing it so large, shows how far engineers may be defective in judgement on subjects a little remote from their own line, and even in his own line, instance his difficulty in its launch, said to have cost £8,000, he having persisted in laying down the keel in a high position requiring launching when my friend, John Scott Russel, strongly counselled him to build the vessel low down, where, with a high tide, it could be floated off. This double blunder of Brunel, as well as the blunder, if not something worse, of Stevenson regarding the Suez Canal, shows how little engineers of the highest standing are to be trusted. Still, the mesmeric or glamour * effect of a confident engineer and eloquent orator at a public meeting is often irresistible, although what they project be highly absurd.
The Great Eastern was just such another great blunder as the erection of this great Bridge would be. They are both steps wide of precedent and beyond experience. It is only by a use, quite unthought of at its erection, that the great ship has not been a great failure from the first. In the case of the Bridge, there is no new purpose that can occur to render it profitable.
There is still another consideration of great importance to the shareholders. Seeing the very frightful and dangerous appearances of the Bridge, so slim and raised up in mid air, would people not prefer another route to that of the North British? Would the North British then find it profitable to use it? Would not the inhabitants of Newport prefer the safer water conveyance? In the case of accident, and one girder slipping off by the centrifugal impetus of a heavy train, would not the jerk and connected flooring bring the whole down like a pack of cards or dominoes placed on end in line? Also, in the case of war could not a mischievous enemy at the mouth of the Firth, during the night and a making tide, drop a few explosive carcasses, joined together by ropes, to float up, and, becoming entangled with the Bridge piers, blow it up?
Taking all these considerations into view, the erection of the proposed Bridge of Dundee, and not higher up the river — the natural place which common sense points out — would be a rather precarious undertaking, while the maintenance of it afterwards would be attended with so much risk and danger that I should think it prudent of the Bridge Company, should they persist in adopting this very ill-advised line, to take that designation of ‘limited’.
With regard to a bridge at Newburgh, it would be of great advantage to have it a low bridge. Perhaps the Perth people might be made to consent, provided that they were paid yearly one amount of their present shore dues, which would not be much, as few masted vessels now go up. Steamers without masts are by far the most economic vessels for going up the narrow and crooked river to Perth, and a masted vessel is often required to be towed up by a steamer. Or even a drawbridge could be opened for an hour at high water for a time till the practice of using masted vessels up to Perth fell off, and only steamboats used. It is only about high water that a small masted vessel can proceed up or down the narrow river at Newbridge. Here a small local, even doubtful, advantage should give place to a great general good.
Let me not be misunderstood. My great desire is to place Dundee upon the most advantageous line of rail for the north and south and east and west communication in Scotland at the least cost or danger.
I am &c.
28 December 1869
* A word of the same meaning as the old Scots word glamour, so far as I know, is not to be found in any other language. The new term mesmerism, mesmeric, approaches it. This is one of the many proofs of the superiority of the Scottish mind.
(Mr Matthew’s objections to the bridge in an engineering point of view are such as the engineers who are ready to undertake the contract for its erection have no doubt fully considered. Mr Matthew has marshalled together all the possibilities of accident in such a way as to seem very frightful, but if we put together all the similar possibilities of accident to a steamboat crossing the river would any one ever venture to the other side? Would it not be easy, also, to give such a catalogue of possibilities of danger in walking on the street as would frighten any nervous person from going out of doors? As to the liability of the shareholders Mr Matthew seems to overlook that the Bridge is to be maintained and worked after erection by the North British Railway Company. – Ed DA.)