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| {{Use British English|date=October 2013}}
| | Ed is what individuals contact me and my wife doesn't like it at all. What me and my family members adore is to climb but I'm thinking on beginning some thing new. For a whilst I've been in Alaska but I will have to move in a year or two. For many years she's been operating as a travel agent.<br><br>Here is my web page ... psychic love readings ([http://afeen.fbho.net/v2/index.php?do=/profile-210/info/ http://afeen.fbho.net/]) |
| {{For|William McGonagall's poem on this subject|The Tay Bridge Disaster}}
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| {{Infobox rail accident
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| | title = Tay Bridge disaster
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| | image = Tay bridge down.JPG
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| | caption =
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| | date = 28 December 1879
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| | time = 7:16 pm
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| | location = [[Dundee]]
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| | coordinates=
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| | country = Scotland
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| | line = [[Edinburgh to Aberdeen Line]]
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| | operator = [[North British Railway]]
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| | type =
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| | cause = Structural failure
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| | trains = 1
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| | pax = 70
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| | deaths = 75 estimate, 60 known dead
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| | injuries = 0
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| | footnotes = [[List of rail accidents in the United Kingdom|List of UK rail accidents by year]]
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| }}
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| The '''Tay Bridge disaster''' occurred during a violent storm on 28 December 1879 when the first [[Tay Rail Bridge]] collapsed while a train was passing over it from [[Wormit]] to [[Dundee]], killing all aboard. The bridge – designed by [[Thomas Bouch|Sir Thomas Bouch]] – used [[lattice girder]]s supported by iron piers, with [[cast iron]] columns and [[wrought iron]] cross-bracing. The piers were narrower and their cross-bracing was less extensive and robust than on previous similar designs by Bouch.
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| Bouch had sought expert advice on "[[wind loading]]" when designing a proposed rail bridge over the [[Firth of Forth]]; as a result of that advice he had made no explicit allowance for wind loading in the design of the Tay Bridge. There were other flaws in detailed design, in maintenance, and in quality control of castings, all of which were, at least in part, Bouch's responsibility.
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| Bouch died within the year, with his reputation as an engineer ruined. Future British bridge designs had to allow for wind loadings of up to 56 pounds per square foot (2.7 kPa). Bouch's design for the [[Forth Rail Bridge]] was not used.
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| ==The bridge==
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| [[File:Original Tay Bridge before the 1879 collapse.jpg|thumb|280px|Original Tay Bridge from the north]] Construction began in 1871 of a bridge to be supported by brick piers resting on bedrock shown by trial borings to lie at no great depth under the river. At either end of the bridge the bridge girders were [[deck truss]]es, the tops of which were level with the pier tops, with the single track railway running on top. However, in the centre section of the bridge (the "high girders") the bridge girders ran as [[through truss]]es above the pier tops (with the railway inside them) in order to give the required clearance to allow passage of sailing ships to [[Perth, Scotland|Perth]].<ref>Bridge design is described (intermittently) in Minutes of Evidence pp. 241-271(H Law); the bridge design process in Minutes of Evidence pp. 398-408 (Sir Thomas Bouch)</ref>
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| Bedrock actually lay much deeper and Bouch had to redesign the bridge, with fewer piers and correspondingly longer span girders. The pier foundations were now constructed by sinking brick-lined wrought-iron caissons onto the riverbed, and filling these with concrete. To reduce the weight these had to support, Bouch used open lattice iron skeleton piers (each pier had multiple cast-iron columns taking the weight of the bridging girders, with wrought iron horizontal braces and diagonal tiebars linking the columns of the pier to give rigidity and stability). The basic concept was well known, but for the Tay Bridge, the pier dimensions were constrained by the caisson. There were 13 high girders spans; to accommodate thermal expansion, at only 3 of their 14 piers was there a fixed connection to the girders; there were therefore 3 divisions of linked high girder spans, the spans in each division being structurally connected to each other, but not to neighbouring spans in other divisions.<ref name="Law">Minutes of Evidence pp. 241-271(H Law)</ref> The southern and central divisions were nearly level but the northern division descended towards Dundee at gradients of up to 1 in 73.<ref>Report of Court of Inquiry – Appendix 3</ref>
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| The bridge was built by [[Gilkes Wilson and Company|Hopkin Gilkes and Company]], a [[Middlesbrough]] company which had worked previously with Bouch on iron viaducts. Gilkes, having first intended to produce all ironwork on Teesside, used a foundry at Wormit to produce the cast-iron components, and to carry out limited post-casting machining. Gilkes were in some financial difficulty ; they ceased trading in 1880, but had begun liquidation in May 1879, before the disaster.<ref>{{London Gazette |issue=24724 |startpage=3504 |accessdate=1 March 2012 |date=20 May 1879 }}</ref> Bouch's brother had been a director of Gilkes,{{#tag:ref| Mr Gilkes and the Bouches had been colleagues on the [[Stockton and Darlington]] 30 years previously |group=note}} and on his death in January 1876 Bouch had inherited Gilkes shares valued at £35,000 but also a guarantee of £100,000 of Gilkes borrowings and been unable to extricate himself.<ref name="STB440">Mins of Ev p. 440 (Sir T Bouch)</ref>
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| The change in design increased cost and necessitated delay, intensified after two of the high girders fell when being lifted into place in February 1877, but the first engine crossed the bridge in September 1877. A Board of Trade inspection was conducted over three days of good weather in February 1878; the bridge was passed for use by passenger traffic subject to a 25 mph speed limit, but the inspection report noted: <blockquote>'... When again visiting the spot I should wish, if possible, to have an opportunity of observing the effects of high wind when a train of carriages is running over the bridge ...'.<ref>{{cite web|url=http://www.railwaysarchive.co.uk/docsummary.php?docID=381 |title=Tay Bridge Disaster: Appendix to the Report Of The Court of Inquiry (page 42) |date= |accessdate=20 September 2012}}</ref></blockquote>
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| The bridge was opened for passenger services on 1 June 1878. Bouch was knighted in June 1879 soon after Queen Victoria had used the bridge.
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| ==The disaster==
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| On the evening of 28 December 1879, a [[European windstorm|violent storm]] (10 to 11 on the [[Beaufort Scale]]) was blowing virtually at right angles to the bridge.<ref name="CS24">Mins of Ev p. 24 (Captain Scott)</ref> Witnesses said the storm was as bad as any they had seen in the 20–30 years they had lived in the area;<ref name="JBL15">Mins of Ev p. 15 (James Black Lawson)</ref><ref name="CJG33">Mins of Ev p. 33 (Capt John Greig)</ref> one called it a hurricane, as bad as a typhoon he had seen in the China Sea.<ref name="GC18">Mins of Ev p. 18 (George Clark)</ref> The wind speed was measured at Glasgow – {{convert|71|mph|km/h|0|abbr=on}} (averaged over an hour) – and Aberdeen, but not at Dundee. Higher windspeeds were recorded over shorter intervals, but at the inquiry an expert witness warned of their unreliability, and declined to estimate conditions at Dundee from readings taken elsewhere.<ref name="RHS392">Mins of Ev p. 392 (Robert Henry Scott, MA FRS, Secretary to the Meteorological Council)</ref> (One modern interpretation of available information suggests winds were gusting to {{convert|80|mph|km/h|0|abbr=on}}.<ref name="Burt, P. J. A. 2004">Burt, P. J. A. (2004), The great storm and the fall of the first Tay Rail Bridge. Weather, 59: 347–350 {{doi|10.1256/wea.199.04}}</ref>)
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| Usage of the bridge was restricted to one train at a time by a [[signalling block system]] using a baton as a [[token (railway signalling)|token]]. At 7:13 pm a train from the south slowed to pick up the baton from the signal cabin at the south end of the bridge, then headed out onto the bridge, picking up speed. The signalman turned away to log this and then tended the cabin fire but a friend present in the cabin watched the train: when it had got about {{convert|200|yd|m|0|sigfig=1|about}} from the cabin he saw sparks flying from the wheels on the east side {{#tag:ref| also seen on the previous train;<ref name="JB79">Mins of Ev p. 79 (John Black)</ref> the wind was pushing the wheel flanges into contact with the running rail – the guard rails protecting against derailment were slightly higher than and ''inboard'' of the running rails<ref name="JB79"/> see [http://openlearn.open.ac.uk/file.php/3782/!via/oucontent/course/239/tay_1_021i.jpg] showing 4 rails with the inner two unpolished : (this arrangement would catch the good wheel where derailment was by disintegration of a wheel- a real risk before steel wheels e.g. [[Shipton-on-Cherwell train crash]])|group=note}}, this continued for no more than three minutes, by then the train was in the high girders;<ref name="JW7">Mins of Ev p. 7 (John Watt)</ref> then "there was a sudden bright flash of light, and in an instant there was total darkness, the tail lamps of the train, the sparks and the flash of light all ... disappearing at the same instant"<ref name="RCI9"/> The signalman saw (and when told believed) none of this {{#tag:ref| not Rolt’s account but see<ref name="TB5"/>|group=note}} but when the train didn't appear on the line off the bridge into Dundee he tried to talk to the signal cabin at the north end of the bridge, but found that all communication with it had been lost.<ref name="TB5">Mins of Ev p. 5 (Thomas Barclay)</ref>
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| [[File:North British Railway locomotive 224.jpg|thumb|280px|The locomotive was dropped during retrieval, but eventually recovered and returned to service.]]
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| Not only was the train in the river, but so were the high girders, and much of the ironwork of their supporting piers.<ref>Photographs of the damaged piers and of recovered wreckage are accessible at [http://digital.nls.uk/scottish-bridges/pageturner.cfm?id=74465507]</ref> Divers exploring the wreckage later found the train still within the girders, with the engine in the fifth span of the southern 5-span division.<ref name="ES39">Mins of Ev p. 39 (Edward Simpson)</ref> 56 tickets for Dundee had been collected from passengers on the train before crossing the bridge; allowing for season ticket holders, tickets for other destinations, and for railway employees 74–75 people were believed to have been on the train.<ref name="RCI9">Report of the Court of Inquiry page 9</ref> There were no survivors; there were 60 known victims, but only 46 bodies were recovered, two not until February 1880.<ref>[http://www.scotlandspeople.gov.uk/content/images/famousscots/RCE1880_282_02_006_0093Z.tif Extract from the "Register of Corrected Entries"] (entries added after the [[Fiscal quarter|quarter]]'s register of deaths was closed) from the [[General Register Office for Scotland]]</ref>{{Failed verification|date=November 2013}}
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| ==Court of Inquiry – evidence==
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| A Court of Inquiry (a judicial enquiry under Section 7 of the Regulation of Railways Act 1871 'into the causes of, and circumstances attending' the accident) was immediately set up: [[Henry Cadogan Rothery]], Commissioner of Wrecks, presided, supported by [[William Yolland|Colonel Yolland]] (Inspector of Railways) and [[William Henry Barlow]], President of the [[Institution of Civil Engineers]]. By 3 January 1880, they were taking evidence in Dundee; they then appointed Henry Law (a qualified civil engineer) to undertake detailed investigations. Whilst awaiting his report they held further hearings in Dundee (26 February – 3 March); having got it they sat at Westminster (19 April – 8 May) to consider the engineering aspects of the collapse.<ref>Report of the Court of Inquiry, page 3</ref> By then railway, contractor and designer had separate legal representation, and the NBR had sought independent advice (from [[James Brunlees]] and [[John Cochrane (English civil engineer)|John Cochrane]]{{#tag:ref|obituary at Minutes of the Proceedings, of the Institution of Civil Engineers PART 3 Volume 109, Issue 1892, January 1892, pages 398 - 399 accessible on guest basis by search at <ref name=icevirtuallibrary>{{cite web|title=ICE virtual library|url=http://www.icevirtuallibrary.com}}</ref>|group=note}}, both engineers with extensive experience of major cast-iron structures). The terms of reference did not specify the underlying purpose of the inquiry – to prevent a repetition, to allocate blame, to apportion liability/culpability, or to establish what precisely had happened. This led to difficulties/clashes during the Westminster sessions and when the court reported their findings at the end of June, there was both an Inquiry Report signed by Barlow and Yolland and a minority report by Rothery.
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| ===Other eyewitnesses===
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| Two witnesses, viewing the high girders from the north almost end-on, had seen the lights of the train as far as the 3rd–4th high girder, when they disappeared; this was followed by three flashes from the high girders north of the train. One witness said these advanced to the north end of the high girders with about 15 seconds between first and last;<ref name="AM19">Mins of Ev p. 19 (Alexander Maxwell)</ref>{{#tag:ref| Maxwell, an engineer, thought the flashes too red to be friction sparks unless tinged by ignition of gas escaping from the [[town gas]] main on the bridge|group=note}} the other that they were all at the north end, with less time between.<ref name="WAC19">Mins of Ev p. 19 (William Abercrombie Clark)</ref> A third had seen 'a mass of fire fall from the bridge' at the north end of the high girders.<ref name="JBL16">Mins of Ev p. 16 (James Black Lawson)</ref> A fourth said he had seen a girder fall into the river at the north end of the high girders, then a light had briefly appeared in the southern high girders, disappearing when another girder fell; he made no mention of fire or flashes.<ref name="PB53">Mins of Ev p. 53 (Peter Barron)</ref>{{#tag:ref|and the man to whom he talked next remembered being told by Barron that the bridge was in the river, but not that Barron had seen it fall<ref name="HG56">Mins of Ev p. 56 (Henry Gourlay)</ref>|group=note}}
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| 'Ex-Provost' Robertson{{#tag:ref|One of 3 William Robertsons who gave evidence; Provost of Dundee when the bridge opened, a [[Justice of the Peace]] and partner in a major engineering firm in Dundee – "an engineer and therefore able to give evidence with authority..."(Rothery)– a brief biography can be found at<ref>{{cite web|title=http://www.scottisharchitects.org.uk|url=http://www.scottisharchitects.org.uk/architect_full.php?id=204643|accessdate=12 February 2012}}</ref>|group=note}} had a good view of most of the bridge from his house in [[Newport-on-Tay]]{{#tag:ref|details and exact location at<ref>{{cite web|title=http://www.britishlistedbuildings.co.uk|url=http://www.britishlistedbuildings.co.uk/sc-38636-balmore-west-road-/osmap|accessdate=12 February 2012}}</ref>|group=note}} but other buildings blocked his view of the southern high girders. He had seen the train move onto the bridge; then in the northern high girders, before the train could have reached them, he saw ''two columns of spray illuminated with the light, first one flash and then another'' and could no longer see the lights on the bridge{{#tag:ref|one light on each of the 14 piers in or bordering the navigable channel, of which he had been able to see seven<ref name="WR64">Mins of Ev p. 64 (William Robertson)</ref>|group=note}} – the only inference he could draw was that the lit ''columns'' of spray – slanting from north to south at about 75 degrees – were areas of spray lit up by the bridge lights as it turned over.<ref name="WR58">Mins of Ev pp. 58-9 (William Robertson)</ref>
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| ===How the bridge was used – speed of trains and oscillation of bridge===
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| Ex-Provost Robertson had bought a season ticket between Dundee and Newport at the start of November, but became concerned about the speed of north-bound local trains through the high girders, which had been causing perceptible vibration, both vertical and lateral. After complaining on three occasions to the stationmaster at Dundee, with no effect on train speed, from mid-December he had used his season ticket to travel south only, using the ferry for north-bound crossings.
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| He had timed the train with his pocket watch; to give the railway the benefit of the doubt he had rounded up to the nearest 5 seconds. The measured time through the girders ({{convert|3149|ft|m|0|abbr=on}}) was normally 65 or 60 seconds{{#tag:ref| he should have measured 85 or 90 seconds if the 25 mph limit was being observed, 60 seconds is almost 36 mph, 50 seconds almost 42 mph - the bridge had been tested at up to 40 mph<ref name="MGH373">Mins of Ev p. 373 (Major-General Hutchinson)</ref>|group=note}}, twice it had been 50 seconds; he had measured 80 seconds when observing from shore trains crossing the bridge, but not on any train he had travelled on. North-bound local trains were often held up to avoid delaying expresses, and then made up time over the bridge; the gradient onto the bridge at the north prevented similar high speeds on south-bound locals. The movement he observed was hard to quantify, but lateral movement was probably one or two inches; it was definitely due to the bridge, not the train, and the effect was more marked at high speed.
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| Four other train passengers supported his timings but only one had noticed any movement of the bridge.<ref>Mins of Ev (pp. 65-72): Thomas Downing Baxter (speed only), George Thomas Hume (speed only), Alexander Hutchinson (speed and movement) and (p. 88) Dr James Miller (speed only)</ref>{{#tag:ref|A further passenger witness spoke of a 'prancing motion' like that felt descending from [[Beattock Summit]] or [[Shap Summit]](the gradient at the N end of the bridge closely matches the ruling gradients of Beattock and Shap); as counsel for the North British pointed out that motion would be due to train movement<ref>Mins of Ev pp. 85-87 (John Leng)</ref>|group=note}} The Dundee stationmaster had passed Robertson's complaint about speed (he had been unaware of any concern about oscillation) on to the drivers and then checked times cabin to cabin (at either end of the bridge the train was travelling slowly to pick up or hand over the baton); he had never checked speed through the high girders.<ref>Mins of Ev pp. 72-76 (James Smith)</ref>
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| Painters who had worked on the bridge in mid-1879 said that the bridge shook when a train was on it;<ref>Mins of Ev pp. 88-97 (David Pirie, Peter Robertson, John Milne, Peter Donegany, David Dale, John Evans)</ref>{{#tag:ref|They had never worked on a lattice girder bridge before; from disinterested recollections of the viaducts on the Stainmore line<ref>{{cite web|title=Stainmore story - the viaducts|url=http://www.stainmore150.co.uk/stainmore_story/viaducts.html |accessdate=14 February 2012}}</ref><ref>{{cite web|title=Don't Look Down - the story of Belah viaduct|url=http://www.forgottenrelics.co.uk/bridges/belah.html|accessdate=14 February 2012}}</ref> some noise and vibration should be expected, even on well-founded bridges |group=note}} when a train entered the southern high girders the bridge had shaken at the north end, both east-west and (more strongly) up-and-down.<ref>Mins of Ev p. 91 (Peter Donegany)</ref> The shaking was worse when trains were going faster, which they did: 'when the Fife boat was nearly over and the train had only got to the south end of the bridge it was a hard drive'.<ref>Mins of Ev p. 95 (John Evans)</ref> A joiner who had worked on the bridge May–October 1879 also spoke of a lateral shaking, more alarming than the up-and-down motion and greatest at the southern junction between the high girders and the low girders. He was unwilling to quantify the amplitude of motion; when pressed he offered 2-3 inches, when pressed further he would only say that it was distinct, large, and visible.<ref>Mins of Ev pp. 101-103 (Alexander Stewart)</ref> One of the painters' foremen however said the only motion he had seen had been north-south, and that this had been less than half an inch.<ref>Mins of Ev pp. 124-5 (Edward Simpson)</ref>
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| ===How the bridge was maintained – chattering ties and cracked columns===
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| NBR maintained the railway but Bouch was retained by them to supervise maintenance of the bridge by a bridge inspector (Henry Noble: a bricklayer by trade, not an engineer<ref name="HAN215-225">Mins of Ev pp. 215-225 (Henry Abel Noble)</ref>) who had worked for Bouch during construction.<ref name="STB409-10">Mins of Ev pp. 409-10 (Sir Thomas Bouch)</ref> Whilst checking pier foundations to see if the river bed was being scoured from under them Noble had become aware that some diagonal tie bars were 'chattering',{{#tag:ref|"any of these tie-bars formed by two flat bars of iron are naturally a little out of line because they cross each other, and if they were loose and if there was any vibration it would make one bar strike against another, consequently you would have the noise of one piece of iron hitting against the other"<ref name="FWR370-3">Mins of Ev pp. 370-3 (Frederic William Reeves)</ref>|group=note}} and in October 1878 had began remedying this. Diagonal bracing was by flat bars running from one lug at a column section top to two sling plates bolted to a lug at the base of the equivalent section on an adjacent column. Bar and sling plates all had a matching longitudinal slot in them; the tie bar was placed between the sling plates with all three slots aligned and overlapping and a gib driven through all three slots and secured. Two cotters (metal wedges) were then positioned to fill the rest of the slot overlap, and driven in hard to put the tie under tension. On the chattering ties the cotters were loose and even if driven fully in would not fill the slot and put the bar under tension.(He had assumed the cotters were too small and hadn't been driven up hard in the first place.) By fitting an additional packing piece between loose cotters and driving the cotters in he had retightened loose ties and stopped them chattering. There were over 4,000 gib and cotter joints on the bridge; only about 100 had had to be retensioned, most in October–November 1878. On his last check (December 1879) only two ties had needed attention, both on piers north of the high girders.
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| He had found cracks in four column sections; one under the high girders, three to the north of them. These had been bound with wrought iron hoops. Bouch had been consulted about the cracked columns, but not the chattering ties.<ref>Mins of Ev p. 219 (Henry Abel Noble), confirmed by pp. 427-429 (Sir Thomas Bouch)</ref>
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| ===How the bridge was built – The Wormit Foundry===
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| The workers at the Wormit foundry complained that the columns had been cast using '[[Middlesbrough|Cleveland]] iron', which always had scum on it: it was less easy to cast than 'good Scotch metal'<ref>Mins of Ev p. 103 (Richard Baird)</ref>{{#tag:ref|the experts agreed with them, but – they pointed out - Cleveland foundries managed to produce quality castings|group=note}} and more likely to give defective castings. Moulds were damped with salt water,<ref>Mins of Ev p. 107 (Richard Baird)</ref> cores were inadequately fastened, and moved, giving uneven column wall thickness.<ref>Mins of Ev p119 (David Hutton)</ref> The foundry foreman explained that where lugs had been imperfectly cast, the missing metal was added by 'burning on';{{#tag:ref|forming a mould around the defective lug, heating that end of the column and adding molten metal to fill the mold and – hopefully - adequately fuse with rest of the column|group=note}} blowholes and other casting defects in the column if minor had been filled with 'Beaumont egg'{{#tag:ref| beeswax, fiddler's rosin, fine iron filings and lampblack, melted together, poured into the hole and allowed to set "the nature of Beaumont egg is that it appears to be metal when rubbed with a stone"<ref name="AM206">Mins of Ev p. 401 (Alexander Milne)</ref>|group=note}} which he kept a stock of for that purpose and the casting used.<ref name="FF144-152">Mins of Ev pp. 144-52 (Fergus Fergusson)</ref>
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| ===How the bridge was built – management and inspection===
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| Gilkes' site staff were inherited from the previous contractor. Under the resident engineer there were seven subordinates including a foundry manager. The original foundry manager left before most of the high girders pier column sections were cast; his replacement was also supervising erection of the bridge, and had no previous experience of supervising foundry work.<ref name="GWC164">Mins of Ev p. 164 (Gerrit Willem Camphuis)</ref> He was aware of 'burning on',<ref name="GWC158">Mins of Ev pp. 158-163 (Gerrit Willem Camphuis)</ref> but the use of Beaumont egg had been hidden from him by the foreman;<ref>Mins of Ev p. 208 (Alexander Milne) and p. 211 (John Gibb)</ref> when shown defects in bridge castings said he would not have passed the affected column for use; nor would he have passed columns with noticeably uneven wall thickness.<ref name="GWC164"/> According to his predecessor, burning on had only been carried out on temporary 'lifting columns' used to lift girders into place and not part of the permanent bridge structure;<ref name="FWB185">Mins of Ev p. 185 (Frank Beattie)</ref> this was on the instructions of the resident engineer<ref name="AG280">Mins of Ev p. 280 (Albert Groethe)</ref> who had little foundry experience either, and relied upon the foreman.<ref name="AG298">Mins of Ev p. 298 (Albert Groethe)</ref>
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| Whilst the working practices were the responsibility of Gilkes, their contract with NBR provided that all work done by the contractor was subject to approval of workmanship by Bouch; hence Bouch would share the blame for any resulting defective work being present in the finished bridge. The original foundry foreman (dismissed for drunkenness) vouched for Gilkes personally testing for unevenness in the early castings; "Mr.Gilkes, sometimes once a fortnight and sometimes once a month, would tap a column with a hammer, first on one side and then on the other, and he used to go over most of them in that way sounding them.":<ref name="HS154">Mins of Ev p 154 (Hercules Strachan)</ref> Bouch had spent over £9000 on inspection (his total fee was £10,500<ref name="STB409"/>) but produced no witness who had inspected castings on his behalf. Bouch himself had been up about once a week whilst the design was being changed, but 'afterwards, when it was all going on, I did not go so often'.<ref name="STB418"/>
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| He had his own 'resident engineer' (William Paterson) who looked after construction of the bridge, its approaches, the line to Leuchars and the Newport branch and was also the engineer of the Perth General Station.<ref name="STB418">Mins of Ev p 418 (Sir Thomas Bouch)</ref>- Bouch told the court Paterson's age was 'very much mine', but actually Paterson was 12 years older{{#tag:ref|(born 1810)<ref>-1881 census: National Archive Reference RG number: RG11 Piece: 387 Folio: 14 Page: 37 details for: Croft Bank, West Church, Perthshire</ref> 'perhaps somewhat too advanced in years for a work of this kind' said Rothery|group=note}} and by the time of the Inquiry paralysed and unable to give evidence.<ref name="STB401">Mins of Ev p. 401 (Sir Thomas Bouch)</ref> Another inspector appointed later<ref name="STB401"/> was now in South Australia and also unable to give evidence. Gilkes managers did not vouch for any inspection of castings by Bouch's inspectors<ref name="EG514">Mins of Ev p. 514 (Edgar Gilkes), p. 370 (Frederick William Reeves) and p. 290 (Albert Groethe)</ref> The completed bridge had been inspected on behalf of Bouch for quality of assembly, but after the bridge was painted{{#tag:ref|but before the bridge opened, and before the painter witnesses were on it in summer 1879|group=note}} which would have hidden cracks or signs of burning on (which the inspector said he wouldn't know if he saw).<ref name="GM135">Mins of Ev p. 135 (G Macbeath)</ref>
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| Throughout Mr Noble had been looking after foundations and brickwork.{{#tag:ref|according to Benjamin Baker "all the difficulty is in the foundations. The superstructure of the piers is ordinary everyday work ".<ref name="BB511">Mins of Ev p. 511 (Benjamin Baker)</ref>|group=note}}
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| ==="The evidence of the ruins"===
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| Henry Law had examined the remains of the bridge; he reported defects in workmanship and design detail. Cochrane and Brunlees, who gave evidence later, largely concurred.
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| *The piers had not shifted or settled, but the masonry of the pier bases showed poor adhesion between stone and cement (the stone had been left too smooth, and had not been wetted before adding the cement). The hold-down bolts to which the column bases were fastened were poorly designed, and burst through the masonry too easily.<ref name="HL244-5">Mins of Ev pp. 244-5 (Henry Law)</ref>
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| *The connecting flanges on column sections were not fully faced{{#tag:ref|machined to give smooth flat surfaces fitting snugly against each other |group=note}}; the spigot which should have given positive location of one section in the next was not always present{{#tag:ref|a later witness explained that this could not be checked at the foundry - 'low girder' columns had no spigots<ref>Mins of Ev p. 293 (Albert Groethe)</ref>|group=note}}, and the bolts did not fill the holes. Consequently, the only thing resisting one flange sliding over another was the pinching-down action of the bolts.<ref name="HL245-6 ">Mins of Ev pp. 245-6 (Henry Law)</ref> This was reduced as boltheads and nuts were unfaced – some nuts had burrs up to 0.05 inch on them (he produced an example). This prevented any holding-down power, and if such a nut was used at a column base joint and the burr subsequently crushed, there would be over 2 inches free play at the top of the column. The nuts used were abnormally short and thin.<ref name="HL255">Mins of Ev p. 255 (Henry Law)</ref>
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| *The column bodies were of uneven wall thickness, as much as ½ inch out; sometimes because the core had shifted, sometimes because the two halves of the mould were misaligned. Thin metal was undesirable, both in itself and because (since it cooled quicker) it would be more vulnerable to [[casting defects#Pouring metal defects|'cold shuts']]<blockquote>Here ''(producing a specimen)'' is a nodule of cold metal which has been formed. The metal, as one would expect in the thin part, is very imperfect. Here is a flaw which extends through the thickness of the metal. Here is another and here is another...It will be found that all the upper side of this column is of that description, perfectly full of air-holes and cinders. There are sufficient pieces here to show that these flaws were very extensive.<ref name="HL247"/></blockquote>Bouch said uneven thickness was unworkmanlike – if he had known he would have taken the best means to cast vertically – but safe.<ref name="STB419">Mins of Ev p. 419 (Sir Thomas Bouch)</ref>
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| *The channel-iron horizontal braces did not butt up against the column body – correct separation was dependent on bolts being tightly nipped up; previous comments about lack of facing applied here also. Because holes in lugs were cast not drilled, their position was more approximate, and some horizontal braces had been site-fitted, leaving burrs up to 3/16th inch.<ref name="HL247">Mins of Ev p. 247 (Henry Law)</ref>
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| *In the diagonal bracing; the gib and cotters were roughly forged and left unfaced, and were much too small to withstand in compression the force the bracing bars could put on them.{{#tag:ref|Law’s sums appear (with the wrong number and units at a crucial point) on p.248 of the Minutes of Evidence; the correct version would seem to be this: The bars had a cross section of 1.625 square inches which should resist more than 8 tons without exceeding 5 ton/square inch, the gibs an area of 0.375 square inch and would fail in compression at about 18 ton/square inch, i.e. somewhat under 7 tons (for completeness; the lugs – total area about 10 square inches – should resist up to 10 tons without exceeding the much lower design limit for cast iron under tension (1 ton/square inch))|group=note}}
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| *On the southernmost fallen pier, every tie bar to the base of one of the columns had had a packing piece fitted .<ref name="HL252">Mins of Ev p.252 (Henry Law)</ref>
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| *The bolt holes for the lugs were cast with a taper; consequently the bolt-lug contact was by the bolt thread bearing against a knife edge at the outer end of the hole. The thread would easily crush and allow play to develop, and the off-centre loading would fail the lugs at much lower loads than if the hole was cylindrical.<ref name="HL248">Mins of Ev p.248 (Henry Law)</ref> Cochrane added that the bolt would bend permanently (and slacken its tiebar to about the extent that had had to be taken up by packing pieces) at an even lower loading than the cotters would deform; he had found some bent tiebar bolts.<ref name="JC341-3">Mins of Ev pp. 341-3 (John Cochrane)</ref>
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| *The bracing had failed by the lugs giving way; in nearly every case, the fracture ran through the hole. Law had seen no evidence of 'burnt-on' lugs<ref name="HL248"/> but some lug failures were by lug and a surrounding area of column breaking away from the rest of the column (what would be expected where burning-on had taken place) and on intact columns paint would hide any evidence of burning-on.<ref name="HL318">Mins of Ev p. 318 (Henry Law)</ref>
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| *At some piers, base column sections were still standing; at others base sections had fallen to the west;<ref name="HL263">Mins of Ev p. 263 (Henry Law)</ref> Cochrane added that fallen girders lay on top of the eastern columns, but the western columns on top of the girders; hence the engineers<ref name="HL263"/><ref name="JC345"/><ref name="DWP467">Mins of Ev p. 467 (Dr William Pole)</ref> concurred that the bridge had broken up before it fell, not as a consequence of it toppling.
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| *From marks on the south end of the southernmost high girder, it had moved bodily eastwards for about 20 inches across the pier before falling to the north.<ref name="HL256">Mins of Ev p. 256 (Henry Law)</ref>
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| ===Bridge materials===
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| Samples of the bridge materials, both cast and wrought iron, were tested by [[David Kirkaldy]], as were a number of bolts, tiebars, and associated lugs. Both the wrought and cast iron had good strength, while the bolts ''"were of sufficient strength and proper iron."'' <ref name="WP483">Mins of Ev p. 483 (Dr William Pole)</ref>{{#tag:ref|The bolt-maker had gone bankrupt and various disgruntled workmen had alleged that the iron was bad, the bolt-maker’s buyer bribed, and the bolts un-tested.|group=note}} However, both ties and sound lugs failed at loadings of about 20 tons, well below what had been expected. Both ties<ref name="HL263"/> and lugs were weakened by high local stresses where the bolt bore on them.<ref name="HL248"/> Four of the fourteen lugs tested were unsound, having failed at lower than expected loadings. Some column top lugs outlasted the wrought iron, but the bottom lugs were significantly weaker.<ref name="HL303-4 ">[http://openlearn.open.ac.uk/file.php/3782/!via/oucontent/course/239/tay_1_paper2_page1x.pdf Mins of Ev pp. 303-4 (Henry Law) - data can be found at]</ref>
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| ==Court of Inquiry – opinions and analysis==
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| ===Windloading===
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| ====Windloading assumed in design====
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| Bouch had designed the bridge, assisted in his calculations by [[Allan Stewart (engineer)|Allan Stewart]].{{#tag:ref|obituary at Minutes of the Proceedings of the Institution of Civil Engineers, Part 1 Volume 119, Issue 1895, January 1895, p. 399–400 (accessible on guest basis by search in <ref name=icevirtuallibrary/>)|group=note}} After the accident Stewart had assisted [[William Pole]]{{#tag:ref|obituary at Minutes of the Proceedings of the Institution of Civil Engineers, Part 1 Volume 143, Issue 1901, January 1901, pages 301 - 309 (accessible on guest basis by search in <ref name=icevirtuallibrary/>)|group=note}} in calculating what the bridge should have withstood.{{#tag:ref|presumably design calculations had not been kept; presumably this was normal practice, since the Inquiry did not comment on this|group=note}} On the authority of Stewart they had assumed that the bridge was designed against a wind loading of 20 pounds per square foot (psf) 'with the usual margin of safety'.<ref>p. xiv of Appendix to Report of Inquiry</ref>{{#tag:ref|the Board of Trade expectation was that tensile stress on wrought iron should not exceed 5 ton per square inch; this gave a margin of at least 4 against failure and about 2 against plastic deformation<ref name="JB366">Mins of Ev p. 366 (James Brunlees)</ref>|group=note}} Bouch said that whilst 20 psf had been discussed, he had been 'guided by the report on the Forth Bridge' to assume 10 psf and therefore made no special allowance for wind loading.<ref name="STB420">Mins of Ev p. 420 (Sir Thomas Bouch)</ref>
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| He was referring to advice given by the [[Astronomer Royal]], [[Sir George Biddell Airy]] in 1873 when consulted about Bouch's design for a suspension bridge across the [[Firth of Forth]]; that wind pressures as high as 40 psf might be encountered very locally, but averaged over a 1600 ft span 10 psf would be a reasonable allowance.<ref name="SGA381">Mins of Ev p. 381(Sir George Airy)</ref> This advice had been endorsed by a number of eminent engineers.{{#tag:ref|[[Sir John Hawkshaw]], [[Thomas Elliot Harrison]], [[George Parker Bidder]], and Barlow<ref name="STB405">Mins of Ev p. 405 (Sir Thomas Bouch)</ref>|group=note}} Bouch also mentioned advice given by Yolland in 1869 – that the Board of Trade did not require any special allowance for wind loading for spans less than 200 ft, whilst noting this was for the design of girders not piers.<ref name="STB420"/>{{#tag:ref| factually correct: and the bridge piers ''were'' designed without any special allowance for wind loading; on Pole's sums, if they had supported 200-ft span girders, they would have been 'within code' at 20 psf; nd Cochrane's evidence was that the bridge – if properly executed- would not have failed , which would apply ''a fortiori'' with 200-foot spans.|group=note}}
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| ====Opinions on windloading allowance====
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| Evidence was taken from scientists on the current state of knowledge on wind loading and from engineers on the allowance they made for it. Airy said that the advice given was specific to suspension bridges and the Forth; 40 psf could act over an entire span of the Tay Bridge and he would now advise designing to 120 psf i.e. 30 psf with the usual margin of safety.<ref name="SGA381"/> The highest pressure measured at [[Greenwich]] was 50 psf; it would probably go higher in Scotland. [[Sir George Stokes, 1st Baronet|Sir George Stokes]] agreed with Airy that ‘catspaws’, ripples on the water produced by gusts, could have a width of several hundred yards. Standard wind pressure measurements were of hydrostatic pressure which had to be corrected by a factor of 1.4–2 to give total wind loading – with a 60 mph wind this would be 12.5–18 psf.<ref>Mins of Ev pp. 385-391 (George Stokes)</ref> Pole referred to Smeaton's work, where high winds were said to give 10 psf, with higher values being quoted for winds of 50 mph or above, with the caveat that these were less certain.<ref>Mins of Ev p. 464 (Dr William Pole)</ref>
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| Brunlees had made no allowance for wind loading on the [[Solway viaduct]] because the spans were short and low – if he had had to, he would probably have designed against 30 psf with a safety margin of 4–5 (by limiting strength of iron).<ref name="JB366"/> Both Pole and Law had used a treatment from a book by [[William John Macquorn Rankine|Rankine]].{{#tag:ref|p. 184 of "Useful Rules and Tables relating to Mensuration, Engineering Structures and Machines " 1866 edition (1872 edition at [http://www.archive.org/details/usefulrulesandt01rankgoog])was the reference given; the original publication "On the Stability of Factory Chimneys" p. 14 in the Proceedings of the Philosophical Society of Glasgow vol IV [http://www.archive.org/details/proceedingsofphi60phil] gives the authority for the high wind pressure|group=note}} Law gave Rankine's statement on the same page that the highest wind pressure seen in Britain was 55 psf as the reason for designing to 200 psf (i.e. 50 psf with a safety factor of 4); " in important structures, I think that the greatest possible margin should be taken. It does not do to speculate upon whether it is a fair estimate or not".<ref>Mins of Ev p. 321 (Henry Law)</ref> Pole had ignored it because no reference was given; he did not believe any engineer paid any attention to it when designing bridges;<ref>Mins of Ev p. 471 (Dr William Pole)</ref> he thought 20 psf a reasonable allowance; this was what [[Robert Stephenson]] had assumed for the [[Britannia Bridge]]. [[Benjamin Baker (engineer)|Benjamin Baker]] said he would design to 28 psf with a safety margin, but in 15 years of looking he had yet to see wind overthrow a structure that would withstand 20 psf. He doubted Rankine's pressures because he was not an experimentalist; told that the data were observations by the [[Regius Professor]] of Astronomy at [[Glasgow University]] {{#tag:ref|[[John Pringle Nichol]] (named in Rankine's manuscript); Rankine had been Regius Professor of Civil Engineering there|group=note}}he doubted that the Professor had the equipment to take the readings.<ref>Mins of Ev pp. 509-10 (Benjamin Baker)</ref>
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| ====Baker's analysis====
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| Baker argued that the wind pressure on the high girders had been no more than 15 psf, from the absence of damage to vulnerable features on buildings in Dundee and the signal cabins at the south end of the bridge. The Inquiry felt that these locations were significantly more sheltered, and therefore rejected this argument. Baker's subsequent work on windpressures at the Forth Rail Bridge site<ref>{{cite book|last=Baker|first=Benjamin|title=The Forth Bridge|year=1884|location=London|pages=47|url=http://archive.org/details/cihm_00842}}</ref> showed meteorologists ''were'' overestimating,<ref>{{cite journal|last=Stanton|first=T E|title=Experiments on Wind Pressure|journal=Minutes of Proceedings of the Institution of Civil Engineers|date=January 1908|volume=171|pages=175–200}}</ref> but his 15 psf might have over-interpreted the data.{{#tag:ref| His most developed example was a pane of glass in a signal cabin
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| * taking the wind at near ground level at the southern shore to be the same as 80 ft above the Tay in mid-firth because there was quite as much disturbance of the ballast (the Inquiry rejected this assumption and therefore Baker's conclusion)
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| * the pressure on the window pane was the same as the wind loading pressure (not valid in the absence of any evidence that leeward windows were open; both Barlow and Rothery corrected him on this<ref>Mins of Ev p. 508 (Benjamin Baker)</ref>)
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| * from work he had previously done on glass of other dimensions the pane would fail at 18 psf (the inquiry did not discuss this, but the sum seems over-precise given the variable failure pressure of outwardly identical panes of glass<ref>{{cite book|last=Brown|first=W G|title=CBD-132 Glass Thickness for Windows|year=1970|publisher=National Research Council Canada - Institute for Research in Construction|url=http://www.nrc-cnrc.gc.ca/eng/ibp/irc/cbd/building-digest-132.html}}</ref>)|group=note}}
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| ===Opinions on bridge components===
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| Law had numerous criticisms of the bridge design, some echoed by other engineers:
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| *He thought the piers should have been wider (both to counteract toppling and to increase the horizontal component forces the tiebars could withstand) and rectangular (to increase the number of tiebars directly resisting lateral forces); at the very least there should have been lateral bracing between the outermost columns of the piers.<ref name="HL254">Mins of Ev p. 254 (Henry Law)</ref>
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| *The lug holes should have been drilled and the tiebars secured by pins filling the holes (rather than bolts)<ref name="HL255"/> (Cochrane had not been surprised that boltholes had been cast conical; moulders were notorious for this, unless you stood over them. Even so he would not rely on supervision or inspection, he would have the holes bored or reamed to ensure they were cylindrical – it had an important bearing on the stability of the structure.<ref name="JC341"/> Pole – called by Bouch's counsel – agreed.<ref name="WP478">Mins of Ev p. 478 (Dr William Pole)</ref> Bouch said if he had known the holes were cast conical he would have had them bored or reamed.<ref name="STB409">Mins of Ev p. 409 (Sir Thomas Bouch)</ref> Gilkes said casting lug holes conical would have been done ''as a matter of course, and unless attention had been drawn to it, it would not be thought then so important as we think it now''.<ref name="EG521">Mins of Ev p. 521 (Edgar Gilkes)</ref>
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| *Cast-on lugs tended to make unsound castings (Cochrane said he had seen examples in the bridge ruins<ref name="JC341">Mins of Ev p. 341 (John Cochrane)</ref>) and had prevented facing of the outer side of flanges.<ref name="HL254"/> Cochrane added that their use meant that columns had had to be cast horizontally rather than vertically, this giving less satisfactory castings;<ref name="JC354">Mins of Ev p. 354 (John Cochrane), confirmed by Edgar Gilkes (Mins of Ev p. 521)</ref> and unless lugs were carefully packed during bolting up they could be damaged or strained.<ref name="JC351">Mins of Ev p. 351 (John Cochrane)</ref> For so tall a pier Gilkes would have preferred some other means of attaching the ties to the columns ''knowing how treacherous a thing cast iron is, but if an engineer gave me such a thing to make I should make it without question, believing that he had apportioned the strength properly''.<ref name="EG521"/> A letter Bouch–Gilkes 22 January 1875 had noted that Gilkes was ''inclined to prefer making the joints of the metal columns the same as on the Beelah and Deepdale''.<ref name="STB404">Mins of Ev p. 404 (Sir Thomas Bouch)</ref> Asked by Rothery why he had departed from the bracing arrangements on the [[Belah Viaduct]], Bouch had referred to changed views on the force of the wind; pressed for other reasons he said Belah-style ties ''were so much more expensive; this was a saving of money''.<ref name="STB429">Mins of Ev p. 429 (Sir Thomas Bouch)</ref>
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| ===Modelling of bridge failure and conclusions drawn===
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| Both Pole and Law had calculated the wind loading needed to overturn the bridge to be over 30 psf (taking no credit for holding-down bolts fastening the windward columns to the pier masonry) <ref name="DWP470">Mins of Ev p. 470 (Dr William Pole)</ref> and concluded that a high wind should have overturned the bridge, rather than cause it to break up (Pole calculated the tension in the ties at 20 psf windloading to be more than the 'usual margin of safety' value of 5 tons per square inch but still only half the failure tension.<ref name="DWP468">Mins of Ev p. 468 (Dr William Pole)</ref>) Pole calculated the wind loading required to overturn the lightest carriage in the train (the second-class carriage) to be less than that needed to overturn the bridge; whereas Law – taking credit for more passengers in the carriage than Pole and for the high girders partially shielding carriages from the wind – had reached the opposite conclusion.<ref name="HL308">Mins of Ev p. 308 (Henry Law)</ref>
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| ====Law: causes were windloading, poor design and poor quality control====
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| Law concluded that the bridge as designed if perfect in execution would not have failed in the way seen<ref name="HL307">Mins of Ev p. 307 (Henry Law)</ref>(Cochrane went further; it 'would be standing now').<ref name="JC346">Mins of Ev p. 346 (John Cochrane)</ref> The calculations assumed the bridge to be largely as designed, with all components in their intended position, and the ties reasonably evenly loaded. If the bridge had failed at lower windloadings, this was evidence that the defects in design and workmanship he had objected to had given uneven loadings, significantly reduced the bridge strength and invalidated the calculation.<ref name="HL308"/> Hence
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| *<blockquote>I consider that in such a structure the thickness of the columns should have been determined, every individual column should have been examined, and not passed until it had received upon it the mark of the person who passed it as a guarantee that it had passed under his inspection</blockquote>
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| *<blockquote>I consider that every bolt should have been a steady pin, and should have fitted the holes to which it was applied, that every strut should have had a firm abutment, that the joints of the columns should have been incapable of movement, and that the parts should have been accurately fitted together, storey by storey upon land and carefully marked and put together again as they had been properly fitted.<ref name="HL308"/></blockquote>
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| ====Pole: causes were windloading and impact of derailed carriages====
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| Pole held that the calculation was valid; the defects were self-correcting or had little effect, and some other reason for the failure should be sought.<ref name="DWP470"/> It was the cast iron lugs which had failed; cast iron was vulnerable to shock loadings, and the obvious reason for a shock loading on the lugs was one of the carriages being blown over and into a bridge girder.<ref name="DWP470"/> Baker agreed, but held the wind pressure was not sufficient to blow over a carriage; derailment was either wind-assisted by a different mechanism or coincidental.<ref name="BB512">Mins of Ev p. 512 (Benjamin Baker)</ref> (Bouch's own view that collision damage to the girder was the sole cause of bridge collapse<ref name="STB415">Mins of Ev p. 415 (Sir Thomas Bouch)</ref> found little support).
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| ===="Did the Train strike the Girders?"====
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| Bouch's counsel called witnesses last; hence his first attempts to suggest derailment and collision were made piecemeal in cross-examination of universally unsympathetic expert witnesses. Law had 'not seen anything to indicate that the carriages left the line' (before the bridge collapse)<ref name="HL266">Mins of Ev p. 266 (Henry Law)</ref> nor had Cochrane<ref name="JC345">Mins of Ev p. 345 (John Cochrane)</ref> nor Brunlees.<ref>Evidence of James Brunlees p.362 – Mins of Ev</ref> The physical evidence put to them for derailment and subsequent impact of one or more carriage with the girders was limited. It was suggested that the last two vehicles (the second-class carriage and a brake van) which appeared more damaged were those derailed, but (said Law) they were of less robust construction and the other carriages were not unscathed.<ref name="HL329">Mins of Ev p. 329 (Henry Laws)</ref> Cochrane and Brunlees added that both sides of the carriages were damaged ''very much alike''.<ref name="JC346"/><ref name="JB362">Mins of Ev p. 362 (James Brunlees)</ref>
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| Bouch pointed to the rails and their chairs being smashed up in the girder holding the last 2 carriages, to the axle-box of the second-class carriage having become detached and ending up in the bottom boom of the eastern girder,<ref name="JW441">Mins of Ev p. 441 (James Waddell)</ref> to the footboard on the east side of the carriage having been completely carried away, to the girders being broken up, and to marks on the girders showing contact with the carriage roof,<ref name="STB415-6">Mins of Ev pp. 415-6 (Sir Thomas Bouch)</ref> and to a plank with wheel marks on it having been washed up at Newport but unfortunately then washed away.<ref name="STB423">Mins of Ev p. 423 (Sir Thomas Bouch)</ref> Bouch's assistant gave evidence of two sets of horizontal scrape marks (very slight scratches in the metal or paint on the girders) matching the heights of the roofs of the last two carriages, but did not know the heights he claimed to be matched.<ref name="CM430">Mins of Ev p. 430 (Charles Meik)</ref> At the start of one of these abrasions, a rivet head had lifted and splinters of wood were lodged between a tie bar and a cover plate. Evidence was then given of flange marks on tie bars in the fifth girder (north of the two rearmost carriages), the 'collision with girders' theory being duly modified to everything behind the tender having derailed.<ref name="JW441"/>
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| However, (it was countered) the girders would have been damaged by their fall regardless of its cause. They had had to be broken up with dynamite before they could be recovered from the bed of the Tay (but only after an unsuccessful attempt to lift the crucial girder in one piece which had broken many girder ties).<ref name="JH438-9">Mins of Ev pp. 438-9 (John Holdsworth Thomas)</ref> The tender coupling (which clearly could not have hit a girder) had also been found in the bottom boom of the eastern girder.<ref name="STB422">Mins of Ev p. 422 (Sir Thomas Bouch)</ref> Two marked fifth girder tie bars were produced; one indeed had 3 marks, but two of them were on the underside.<ref name="JW443">Mins of Ev p. 443 (James Waddell)</ref> [[Dugald Drummond]], responsible for NBR rolling stock, had examined the wheel flanges and found no 'bruises' – expected if they had smashed up chairs. If the second-class carriage body had hit anything at speed, it would have been 'knocked all to spunks' without affecting the underframe.{{#tag:ref|In 1871 at Maryhill an NBR train running at 20-25 mph was fouled by a travelling crane on the opposite line: for details of the damage caused see <ref>{{cite web|title= BoT_Maryhill1871.pdf |url=http://www.railwaysarchive.co.uk/documents/BoT_Maryhill1871.pdf|accessdate=27 March 2012}}</ref>|group=note}} Had collision with the eastern girder slewed the frame, it would have presented the east side to the oncoming brake van, but it was the west side of the frame that was more damaged. Its eastern footboard had not been carried away; the carriage had never had one (on either side). The graze marks were at 6–7 ft above the rail, and 11 ft above the rail and did not match carriage roof height.<ref name="DD453-4">Mins of Ev pp. 453-4 (Dugald Drummond)</ref> Drummond did not think the carriages had left the rails until after the girders began to fall, nor had he ever known a carriage (light or heavy) to be blown over by the wind.<ref name="DD459">Mins of Ev p. 459 (Dugald Drummond)</ref>
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| ==Court of Inquiry findings==
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| The three members of the court failed to agree a report although there was much common ground:<ref>Report of Court of Inquiry pp. 15-16, unless referenced otherwise</ref>
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| ===Contributory Factors===
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| * neither the foundations nor the girders were at fault
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| * the quality of the wrought iron, whilst not of the best, was not a factor
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| *the cast iron was also fairly good, but presented difficulty in casting
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| * the workmanship and fitting of the piers was inferior in many respects
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| *the cross bracing of the piers and its fastenings were too weak to resist heavy gales. Rothery complained that the cross-bracing was not as substantial or as well-fitted as on the Belah viaduct;<ref name="RCI43-4">Report of Mr Rothery pp. 43-4</ref> Yolland and Barlow stated that the weight/cost of cross-bracing was a disproportionately small fraction of the total weight/cost of ironwork<ref name="RCI13">Report of Court of Inquiry p. 13</ref>
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| * there was insufficiently strict supervision of the Wormit foundry (a great apparent reduction of strength in the cast iron was attributable to the fastenings bringing the stress on the edges of the lugs, rather than acting fairly on them)<ref name="RCI13"/>
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| *supervision of the bridge after completion was unsatisfactory; Noble had no experience of ironwork nor any definite instruction to report on the ironwork
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| *nonetheless Noble should have reported the loose ties.{{#tag:ref| Yolland and Barlow say that if he had there would have been ample time to put in stronger ties and fastenings, which is difficult to reconcile with the weak point having been the integrally cast lugs |group=note}} Using packing pieces might have fixed the piers in a distorted form.
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| *the 25 mph limit had not been enforced, and frequently exceeded.
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| Rothery added that, given the importance to the bridge design of the test borings showing shallow bedrock, Bouch should have taken greater pains, and looked at the cores himself.<ref name="RCI41">Report of Mr Rothery pp. 41</ref>
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| ==="True Cause of the Fall of The Bridge"===
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| According to Yolland and Barlow ''the fall of the bridge was occasioned by the insufficiency of the cross-bracings and fastenings to sustain the force of the gale on the night of December 28th 1879 ... the bridge had been previously strained by other gales''.<ref name="RCI15-6">Report of Court of Inquiry pp. 15-16</ref>
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| Rothery agreed, asking "Can there be any doubt that what caused the overthrow of the bridge was the pressure of the wind acting upon a structure badly built and badly maintained?"<ref name="RCI41"/>
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| ===Substantive differences between reports===
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| Yolland and Barlow also noted the possibility that failure was by fracture of a leeward column.<ref name="RCI15-6"/> Rothery felt that previous straining was ''partly by previous gales, partly by the great speed at which trains going north were permitted to run through the high girders'':<ref name="RCI41"/> if the momentum of a train at 25 mph hitting girders could cause the fall of the bridge, what must have been the cumulative effect of the repeated braking of trains from 40 mph at the north end of the bridge?<ref>Report of Mr Rothery p. 40</ref> He therefore concluded – with (he claimed) the support of circumstantial evidence – that the bridge might well have failed at the north end first;<ref name="Report of Mr Rothery p. 30">Report of Mr Rothery p. 30</ref> he explicitly dismissed the claim that the train had hit the girders before the bridge fell.<ref name="Report of Mr Rothery p. 30"/>
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| Yolland and Barlow concluded that the bridge had failed at the south end first; and made no explicit finding as to whether the train had hit the girders.<ref name="RCI15-6"/> They noted instead that apart from Bouch himself, Bouch's witnesses claimed/conceded that the bridge failure was due to a shock loading on lugs heavily stressed by windloading.<ref>Report of the Court of Inquiry p. 15</ref> Their report is therefore consistent with either a view that the train had not hit the girder or one that a bridge with cross-bracing giving an adequate safety margin against windloading would have survived a train hitting the girder.
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| Yolland and Barlow noted "...there is no requirement issued by the Board of Trade respecting wind pressure, and there does not appear to be any understood rule in the engineering profession regarding wind pressure in railway structures; and we therefore recommend the Board of Trade should take such steps as may be necessary for the establishment of rules for that purpose."<ref>Report of the Court of Inquiry p. 16</ref> Rothery dissented, feeling that it was for the engineers themselves to arrive at an ‘understood rule’, such as the French rule of 55 psf or the US 50 psf.<ref>Report of Mr Rothery p. 49</ref>
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| ===Presentational differences between reports===
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| Rothery's minority report is more detailed in its analysis, more willing to blame named individuals, and more quotable, but the official report of the court is a relatively short one signed by Yolland and Barlow.<ref name=RofCofI>{{cite web|title=Tay Bridge Disaster: Report Of The Court of Inquiry and Report of Mr Rothery|url=http://www.railwaysarchive.co.uk/documents/BoT_TayInquiry1880.pdf|accessdate=3 April 2012}}</ref> Rothery said that his colleagues had declined to join him in allocating blame, on the grounds that this was outside their terms of reference. However, previous Section 7 inquiries had clearly felt themselves free to blame ([[Thorpe rail accident]]) or exculpate ([[Shipton-on-Cherwell train crash]]) identifiable individuals as they saw fit, and when Bouch's solicitor checked with Yolland and Barlow, they denied that they agreed with Rothery that "For these defects both in the design, the construction, and the maintenance, Sir Thomas Bouch is, in our opinion, mainly to blame."<ref>"Responsibility for the Accident": Rothery (1880: 44)</ref>
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| ==Aftermath==
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| ===Section 7 Inquiries===
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| No further judicial enquiries under Section 7 of the Regulation of Railways Act 1871 were held until the [[Hixon rail crash]] in 1968 brought into question both the policy of the Railway Inspectorate towards automated level crossings and the management by the Ministry of Transport (the Inspectorate's parent government department) of the movement of abnormal loads. A Section 7 judicial enquiry was felt necessary to give the required degree of independence.<ref>{{cite journal|title=RAILWAYS (ACCIDENT, HIXON)|journal=Hansard|date=17 January 1968|volume= 756|series=House of Commons Debates|pages=cc1782–5|url=http://hansard.millbanksystems.com/commons/1968/jan/17/railways-accident-hixon#S5CV0756P0_19680117_HOC_208|accessdate=1 April 2012}}</ref> The structure and terms of reference were better defined than for the Tay Bridge inquiry. Brian Gibbens, QC was supported by two expert assessors, and made findings as to blame/responsibility but not as to liability/culpability.<ref name="MoT">{{cite book | last=Ministry of Transport | year=1968 | title=Report of the Public Inquiry into the Accident at Hixon Level Crossing on January 6, 1968 | publisher= HMSO | isbn=0-10-137060-1 | url=http://www.railwaysarchive.co.uk/docSummary.php?docID=74 }}</ref>
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| ===Wind Pressure (Railway Structures) Commission===
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| The Board of Trade set up a 5-man commission (Barlow, Yolland, [[Sir John Hawkshaw]], [[William Armstrong, 1st Baron Armstrong|Sir William Armstrong]] and Stokes) to consider what wind loading should be assumed when designing railway bridges.
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| Windspeeds were normally measured in 'miles run in hour' (i.e. windspeed averaged over one hour) so it was difficult to apply [[John Smeaton|Smeaton]]'s table<ref name="Phil. Trans. 1759 51:100-174; doi:10.1098/rstl.1759.0019">{{cite journal|last=Smeaton|first=Mr J|title=An Experimental Enquiry concerning the Natural Powers of Water and Wind to Turn Mills, and Other Machines, Depending on a Circular Motion|journal=Philosophical Transactions of the Royal Society|year=1759|pages=100–174|url=http://rstl.royalsocietypublishing.org/content/51/100.full.pdf|accessdate=30 January 2012}}</ref> which linked wind pressure to current windspeed
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| :<math>P_t = 0.005 (V_t)^2\,</math>
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| where:
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| :<math>P_t</math>is the instantaneous wind pressure (pounds per square foot)
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| :<math>V_t</math>is the instantaneous air velocity in miles per hour
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| By examination of recorded pressures and windspeeds at [[Bidston Hill|Bidston]] Observatory, the commission found<ref>{{cite web|url=http://www.railwaysarchive.co.uk/documents/WindComm_Tay1880.pdf |title=The main text of the Commission's report can be found at |format=PDF |date= |accessdate=27 February 2012}}</ref> that for high winds the highest wind pressure could be represented very fairly,{{#tag:ref|"From ... observations taken at Bidston of the greatest hourly velocity and of the greatest pressure on the square foot during gales between the years 1867 and 1895 inclusive, I find that the average pressure (24 readings) for an hourly run of wind at 70 miles an hour was 45lbs. per square foot. Similarly, the average pressure (18 readings) at 80 miles an hour was 60 lbs. per square foot, and that at 90 miles an hour (only 4 readings) was 71 lbs. per square foot."<ref name="Levens Viaduct">[http://www.railwaysarchive.co.uk/documents/BoT_LevenViaduct1903.pdf Accident report Levens Viaduct 1903],</ref>|group=note}} by
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| :<math>P_m = 0.01 (V_h)^2\,</math>
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| where:
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| :<math>P_m</math>is the maximum instantaneous wind pressure experienced (pounds per square foot)
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| :<math>V_h</math>is the 'miles run in hour' (one hour average windspeed) in miles per hour
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| However, they recommended that structures should be designed to withstand a wind loading of 56 psf, with a safety factor of 4 (2 where only gravity was relied upon). They noted that higher wind pressures had been recorded at Bidston Observatory but these would still give loadings well within the recommended safety margins. The wind pressures reported at Bidston were probably anomalously high because of peculiarities of the site (one of the highest points on the Wirral.<ref name="Metropolitan Borough of Wirral: Bidston Hill">{{Cite document|url=http://www.wirral.gov.uk/my-services/leisure-and-culture/parks-beaches-and-countryside/parks-greenspaces-and-countryside/natural-areas-and-greenspaces|title=Natural Areas and Greenspaces: Bidston Hill|publisher=Metropolitan Borough of Wirral|accessdate=13 June 2010 }}</ref><ref name="The Wirral Hundred/The Wirral Peninsula">{{Cite web|url=http://www.mikekemble.com/mside/wirral.html|first=Mike|last=Kemble|title=The Wirral Hundred/The Wirral Peninsula|accessdate=12 August 2007 }}</ref>): a wind pressure of 30–40 psf would overturn railway carriages and such events were a rarity. (To give a subsequent, well documented example, in 1903 a stationary train ''was'' overturned on the Levens viaduct but this was by a 'terrific gale' measured at [[Barrow in Furness]] to have an average velocity of 100 mph, estimated to be gusting up to 120 mph.<ref name="Levens Viaduct"/>)
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| ===Bridges===
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| A new double-track Tay Bridge was built by the NBR, designed by Barlow and built by [[Sir William Arrol & Co.|William Arrol & Co.]] of Glasgow {{convert|18|m}} upstream of, and parallel to, the original bridge. Work started 6 July 1883 and the bridge opened on 13 July 1887. Sir [[John Fowler (engineer)|John Fowler]] and Sir [[Benjamin Baker (engineer)|Benjamin Baker]] designed the [[Forth Rail Bridge]], built (also by Arrols) between 1883 and 1890. Baker and his colleague Allan Stewart received the major credit for design and overseeing building work.{{#tag:ref|the contractor did his bit- Arrols were also simultaneously involved in building [[Tower Bridge]]; [[William Arrol]] spent Monday and Tuesday at the Forth Bridge, Wednesday at the Tay Bridge, Thursday at his Glasgow works, Friday and some of Saturday at Tower Bridge; Sunday he took off.<ref>{{cite book|last=Thomas|first=John|title=The North British Railway : Volume Two|year=1975|publisher=David & Charles|location=Newton Abbott|isbn=0-7153-6699-8|pages=224}}</ref>|group=note}} The Forth Bridge had a 40 mph speed limit, which was not well observed.<ref>p29 J Thomas op cit</ref>
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| Bouch had also been engineer for the [[North British, Arbroath and Montrose Railway]], which included an iron viaduct over the South Esk. Examined closely after the Tay bridge collapse, the viaduct as built did not match the design, and many of the piers were noticeably out of the perpendicular. After vigorous tests with stationary and rolling loads over a 36 hour period, the structure was seriously distorted and pronounced unsafe.<ref>{{cite web|title=British Listed Buildings:Railway Viaducts over South Esk River, Ferryden|url=http://www.britishlistedbuildings.co.uk/sc-49864-railway-viaducts-over-south-esk-river-|accessdate=1 April 2012}}</ref>
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| Bouch's [[Redheugh Bridge]] built 1871 was condemned in 1896, the structural engineer doing so saying later that the bridge would have blown over if it had ever seen windloadings of 19 psf.<ref>{{cite journal|last=Moncrieff|first=John Mitchell|title=Discussion: Wind-Pressures, and Stresses Caused by the Wind on Bridges|journal=Minutes of the Proceedings of the Institution of Civil Engineers|date=January 1923|volume= 216|series=Part 2|issue=1923|pages=34–56}}</ref>
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| ===Reminders===
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| [[File:Dusk on a sunny summers day across Dundee, Scotland, July 17, 2007.jpg|thumb|right|260px|The current bridge at dusk, with the masonry of one of Bouch's piers silhouetted against the sunlit Firth.]]
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| The locomotive, [[NBR 224 Class|NBR no. 224]], a [[4-4-0]] designed by [[Thomas Wheatley (locomotive engineer)|Thomas Wheatley]] and built at [[Cowlairs]] Works in 1871, was salvaged and repaired, remaining in service until 1919, nicknamed "The Diver"; many superstitious drivers were reluctant to take it over the new bridge.<ref>{{cite book |last=Highet |first=Campbell |title=Scottish Locomotive History 1831-1923 |year=1970 |publisher=[[Allen & Unwin|George Allen & Unwin]] |location=London |isbn=0-04-625004-2 |page=89 }}</ref><ref>{{cite book |last=Prebble |first=John |authorlink=John Prebble |title=The High Girders |year=1959 |origyear=1956 |publisher=[[Pan Books|Pan]] |location=London |isbn=0-330-02162-1 |pages=164, 188 }}</ref><ref>{{cite book |last1=Rolt |first1=L.T.C. |authorlink1=L. T. C. Rolt |last2=Kichenside |first2=Geoffrey M. |title=Red for Danger |edition=4th |year=1982 |origyear=1955 |publisher=[[David & Charles]] |location=Newton Abbot |isbn=0-7153-8362-0 |pages=98,101–2 }}</ref><ref>{{cite book |title=Locomotives of the North British Railway 1846-1882 |year=1970 |publisher=[[Stephenson Locomotive Society]] |page=66 }}</ref> The stumps of the original bridge piers are still visible above the surface of the Tay.{{fact|date=November 2013}} Memorials have been placed at either end of the bridge in Dundee and Wormit.<ref>{{cite web | url=http://www.bbc.co.uk/news/uk-scotland-tayside-central-25527719 | title=BBC, Memorials for those killed in Tay Bridge disaster | publisher=BBC | date=28 December 2013 | accessdate=28 December 2013 | author=BBC}}</ref>
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| ==Works of literature about the disaster==
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| {{Wikisource}}
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| The [[Victorian era|Victorian]] poet [[William Topaz McGonagall]] commemorated this event in his poem ''[[The Tay Bridge Disaster]]'', widely regarded as so bad as to be comical. Likewise, [[Germans|German]] poet [[Theodor Fontane]], shocked by the news, wrote his poem ''[[s:de:Die Brück’ am Tay|Die Brück' am Tay]]''. It was published only ten days after the tragedy happened. ''[[Hatter's Castle]]'', the 1931 novel of [[Scottish people|Scottish]] author [[A. J. Cronin]], includes a scene involving the Tay Bridge Disaster, and the 1942 [[Hatter's Castle (film)|filmed version]] of the book dramatically recreates the bridge's catastrophic collapse. The events of Alanna Knight's 1976 novel ''A Drink for the Bridge'' are based around the disaster. The bridge collapse also figures prominently in [[Barbara Vine]]'s 2002 novel ''[[The Blood Doctor]]''.
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| ==Modern reinterpretations==
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| Various additional pieces of evidence have been advanced in the last 40 years, leading to 'forensic engineering' reinterpretations of what actually happened.<ref>{{cite web|title=OU on the BBC: Forensic Engineering – The Tay Bridge Disaster|url=http://www.open.edu/openlearn/whats-on/ou-on-the-bbc-forensic-engineering-the-tay-bridge-disaster|accessdate=3 April 2012}}</ref>
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| ==See also==
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| * [[David Kirkaldy]]
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| * [[Harry Watts]]
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| * [[List of structural failures and collapses]]
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| * [[List of bridge disasters]]
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| * [[List of wind-related railway accidents]]
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| ==Notes and references==
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| ===Notes===
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| {{Reflist|group=note}}
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| ===References===
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| {{reflist|colwidth=30em}}
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| ===Bibliography===
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| {{refbegin}}
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| * [[John Prebble|Prebble, John]], ''The High Girders: The Story of the Tay Bridge Disaster'', 1956 (published by Penguin Books in 1975) ISBN 0-14-004590-2.
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| * Thomas, John ''The Tay Bridge Disaster: New Light on the 1879 Tragedy'', David & Charles, 1972, ISBN 0-7153-5198-2.
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| * Swinfen, David ''The Fall of the Tay Bridge'', Mercat Press, 1998, ISBN 1-873644-34-5.
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| * McKean, Charles, ''Battle for the North: The Tay and Forth Bridges and the 19th-Century Railway Wars: The Building of the Tay and Forth Bridges and the 19th Century Railway Wars'' Granta 2007.
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| * Lewis, Peter R. ''Beautiful Railway Bridge of the Silvery Tay: Reinvestigating the Tay Bridge Disaster of 1879'', Tempus, 2004, ISBN 0-7524-3160-9.
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| * Rapley, John ''Thomas Bouch : the builder of the Tay Bridge'', Stroud : Tempus, 2006, ISBN 0-7524-3695-3
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| * Lewis, Peter R. ''Disaster on the Dee: Robert Stephenson's Nemesis of 1847'', Tempus Publishing (2007) ISBN 978-0-7524-4266-2
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| * Rothery, Henry ''[http://www.railwaysarchive.co.uk/documents/BoT_TayInquiry1880.pdf Tay Bridge Disaster: Report Of The Court of Inquiry, and Report Of Mr. Rothery, Upon the Circumstances Attending the Fall of a Portion of the Tay Bridge on the 28th December 1879]''. London: [[Her Majesty's Stationery Office]], 1880 {{oclc|30875567}}
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| {{Refend}}
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| ==External links==
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| * [http://digital.nls.uk/scottish-bridges/pageturner.cfm?id=74465507 91 black-and-white photographs] of the wrecked piers of the Tay Bridge showing destroyed piers and girders, wreckage of train and steam engine from [[National Library of Scotland]]
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| * [http://taybridgedisaster.co.uk Tom Martin's engineering analysis of the bridge disaster]
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| * [http://materials.open.ac.uk/about_us/tay_bridge.htm ''Reappraisal of the Tay Bridge disaster''] [[Open University]]
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| * [http://failuremag.com/feature/article/the_tay_bridge_disaster/ The Tay Bridge Disaster] at ''[[Failure Magazine]]''
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| * [http://www.dundeecity.gov.uk/centlib/taybridge/taybridge.htm Dundee local history centre page on the disaster]
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| *[http://www.brand-dd.com/taybrig.html Tay Victims listing {reference only}]
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| *[http://www.semp.us/publications/biot_reader.php?BiotID=489 Firth of Tay Bridge Disaster 1879: Worst Structural Disaster in British History] at Suburban Emergency Management Project
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| * [http://www.railwaysarchive.co.uk/documents/BoT_TayInquiry1880.pdf Tay Bridge Disaster: Report Of The Court of Inquiry]
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| * [http://www.railwaysarchive.co.uk/documents/BoT_TayInquiryAppendix1880.pdf Tay Bridge Disaster: Appendix to the Report Of The Court of Inquiry. Includes a large number of drawings of the bridge, and calculations of the result of wind pressure on the structure]
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| * [http://www.railwaysarchive.co.uk/documents/TaySelect_Minutes1880.pdf Report from the Select Committee on the North British Railway (Tay Bridge) Bill; together with the Proceedings of the Committee and Mins of Ev. All the oral evidence given, reproduced verbatim - <small> a very large file but sometimes a useful corrective to reinterpretation by secondary sources </small>]
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| *[http://www.dundee.ac.uk/archives/ms030.htm The Tay Bridge Collection] at [http://www.dundee.ac.uk/archives/welcome.htm Archive Services, University of Dundee]
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| * [http://www.archives-records-artefacts.com/2013/03/was-disaster-built-into-first-tay-bridge.html Was Disaster Built into the First Tay Bridge?] Article relating to the [[University of Dundee]]'s holdings on the disaster
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| {{European windstorms}}
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| {{Coord|56|26|14.4|N|2|59|18.4|W|type:landmark_region:GB|display=title}}
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| {{Use dmy dates|date=February 2012}}
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| [[Category:Transport in Dundee]]
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| [[Category:Railway accidents in Scotland]]
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| [[Category:Railway accidents in 1879]]
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| [[Category:1879 in Scotland]]
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| [[Category:Bridge disasters in the United Kingdom]]
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| [[Category:Bridge disasters caused by engineering error]]
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| [[Category:Bridge disasters caused by construction error]]
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| [[Category:European windstorms]]
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| [[Category:Transport disasters in Scotland]]
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| [[Category:Engineering failures]]
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| [[Category:Thomas Bouch]]
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