Night the bridge fell down

December 2004

TAY BRIDGE DISASTER
by Gordon Casely

The fall of the Tay Bridge seems to represent one of those points in Scotland’s story where history turns a corner. Endless fascination for the disaster ranks ranks with the night before the execution of Queen Mary and Prince Charles Edward’s decision to turn back at Derby.

When I lodged in Dundee as a young reporter in 1966, just round the corner from Jimmy Spankie in his pre-Grampian Television days, it was evident that for my elderly landlady Elizabeth Smith, the calendar of Dundee was ‘before the bridge’ and ‘after the bridge’, just as the world outside this particular bend in the Tay used AD and BC. Miss Smith’s father was 15 when the bridge fell, and the awesomeness of the tragedy still hung visibly on her.

The opening of the two-mile span joining Dundee with Fife gained its designer a knighthood from a queen “graciously pleased” to pass over it. The nation rejoiced that Scotland had become home to the eighth wonder of the world. Nineteen months later and 125 years ago this month, the bridge blew down in a storm, taking with it a train and all aboard to their deaths. The world stopped in its tracks at the news.

You would be hard pushed now to find anything new on the event, though the occasional item suggesting fresh light on an old tragedy still surfaces. Author and historian John Thomas, whom I had the good fortune to meet several times, told me that in many visits to Register House in Edinburgh where the records of Scotland are kept, he eventually turned up a case of papers from the enquiry into the disaster, documents which merely recorded the inquest, and did not in any way interpret the evidence given. Surprisingly, the box had never been reopened since the 1880 Board of Trade enquiry.

For example, the bridgemaster appointed to oversee maintenance was totally unqualified, and he ‘repaired’ defects using material bought over-the-counter from a Dundee ironmonger. The bridge wasn’t designed to take the sustained winds of 100 mph that could funnel up the Tay. The cast-iron columns spanning the firth were supplied as ‘best iron’, but the foundry omitted to mention that there were three grades of iron – ‘best’, ‘best best’ and ‘best best best’.

Erection of columns was entrusted to an ordinary labourer. The Dutch pile-driving supervisor had never before worked on a bridge. Fourteen viaduct piers were founded on rock; a 15th sat on gravel. You couldn’t make this up.

So as the final train inexorably puffed its way north through Fife on the evening of 28 December 1879, the mightiest bridge in the Empire was hanging by a thread. Minutes later, the Tay Bridge triumphant, 75 souls and a complete express train lay at the bottom of the river.

The disaster on the Tay was not the greatest rail calamity in history, but it evokes a special horror. How could this structure, such a source of profit and pride to its owners, vital key in a masterplan to connect Aberdeen to London, become to land communications what the Titanic became to the high seas?

John Thomas’s diligence produced The Tay Bridge Disaster: new light on the 1879 tragedy, a book published in 1972 that still reads like a thriller. John Prebble had written the best-selling The High Girders of 1956, but it was Thomas who set new standards in Tay Bridge research.

His work was followed in 1985 by a study carried out by Tom Martin, a mathematician with British Steel at Ravenscraig. Martin examined the reliance by bridge designer Sir Thomas Bouch on wind calculations made by the Astronomer Royal at the time, Sir George Airy. Martin’s conclusions showed that Airy seriously miscalculated the effect of a Tayside gale on the structure, and that the bridge would have fallen “even if construction had been perfect”.

From Airy’s work, Bouch assumed that vital bolts would withstand wind pressures of Force Five or Six on the Beaufort Scale. Martin stated: “(The bridge) was really just waiting for a good Force nine or 10 to come along”. The high girders heroically withstood Force 10 to 11 before collapsing.

Meanwhile, Sir George Airy’s other engineering scenarios forecast that Crystal Palace would be “blown apart”, and that a Transatlantic cable could never be laid – and if it was, a signal could not be sent along it.

That the 1880 Board of Trade enquiry into the disaster was a virtual travesty has never been denied. In 1990, a paper by Dundonian Bill Dow to the Scottish panel of the Institute of Civil Engineering suggested that the reason for the unsatisfactory state of enquiry was that the judicial techniques of cross-examination did not follow a logical sequence, and were actually designed to confuse witnesses.

Dow brings to light that the enquiry failed to establish that two of the high girders of the central span had already collapsed during construction. One was left at the bottom of the Tay, while the other was salvaged, straightened and re-erected.

But in the 19 months of operation of the old bridge, this second girder gradually resumed its distorted shape and caused a kink in the trackbed.

On the fateful night, Dow believes, it was a combination of wind and kink which was enough to derail the last carriage of the express, bouncing it on to the bridge superstructure. These sudden blows were enough to fracture vital lugs attaching the high girders to vertical towers, triggering the collapse.

There is no doubt that the circumstances of the fall of the bridge continue to fascinate, Dr Iain Macleod of Strathclyde University was joined some years ago by mathematician Tom Martin in producing a three-dimensional computer analysis of the bridge piers in which the results showed that bolts and bracing were approaching ultimate loads that December night. The advent of the train simply started a domino effect.

Martin concludes that “the disaster was due to commercial pressure”. Designer Sir Thomas Bouch was stuck with his famed reputation of creating cheap and speedily-built iron viaducts. On the Tay, faced with substantial redesign and already over budget, he compromised once too often.

As for the wise, they never trusted the Tay Bridge from the start. A prescient Sir John Fowler, designer of the Forth Bridge, refused to allow any members of his own family to cross it.

GORDON CASELY crosses the Tay Bridge once a week, and reflects that some of the repaired and overhauled girders from the old bridge are still happily and safely functioning in the fabric of the present structure.

This is an article from the December 2004 edition of Leopard Magazine. To read much more like this every month, subscribe to Leopard Magazine.