Donald Trump made a casual reference to aerial fire-fighting, sometimes colloquially known as 'water bombing' (although flame-retardant chemicals are used as well as water). France's Sécurité Civile organisation has 12 Bombardier CL-415 fire-fighting aircraft, each of which has a capacity of 6,140 litres of water or chemicals. They are based in the Midi, far from Paris, because that is where wildfires mainly occur. Fire-fighting aircraft with a capacity up to 12 times as large do exist, but they are not used in France. Apart from the time taken to load up with fluid and reach Paris, such is the air-speed and trajectory of a CL-415, that most of the fluid would not land on Notre Dame. These aircraft are built to tackle wide-area environmental fires, not urban conflagrations. Moreover, the weight of water when released could cause stonework to collapse - possibly onto fire fighters on the ground. The scoop-and-release helicopters used in forest-fire fighting would not carry enough water or provide sufficient continuity of flow to make much difference to a well-established fire that had generated large amounts of heat. For this, a constant jet of water is necessary, pumped over several hours or longer. Failure to cool down the embers can lead to a resumption of the fire.
Cathedral 'disasters' are not uncommon in European history. For instance, the nave of Utrecht cathedral was destroyed by a storm in 1675 and is now a piazza of open ground between the west tower and the surviving chancel. In 1349 the Black Death left Siena cathedral half-built. In the 13th century Wells cathedral was damaged by earthquake and was only saved from collapsing by an ingenious structural bracing system, the famous 'scissors arches'. We recall more easily the loss of part of the roof of York Minster when it was struck by lightning in 1984.
Thinking of the longer term, fire can be considered as part of the challenge of renewal. French national pride, and the concern of wealthy people who want to support European civilisation, will ensure that the resources for rebuilding are made available. There is no shortage of artisans and experts in conservation and repair, especially in France. In fact, with modern methods, access to knowledge, science and training, restorers and artisans are probably better equipped now than at any time in the past. Digital finite-element modelling by engineers can accurately predict stresses and strains on a wrecked building. And, of course, everyone wants to help.
As the aftermath of the fire at York Minster reminds us, at Notre Dame stonework is at risk of collapse. Critically so are ancient painted glass windows, where they have survived. At York Minster, they waved backwards and forwards in the wind until scaffolding could be erected to stabilise them. Hence, a big challenge arises as soon as the ruins are cool enough to work in; a challenge of stabilising what is left. The bracing and buttressing of the mediaeval stone fabric of Notre Dame was arrived at by mason-architects intuitively, with a combination of over-design and under-design. It is now critically at risk of collapse until further bracing can be added. Bracing nowadays is both soft and hard: steel scaffolding and woven polymer bands are used. Much has been learned from post-earthquake consolidation work.
Painted and stained glass in Windsor Castle pays tribute to the fire fighters who fought to save the building during the conflagration of 1992. Similar images can be found in the windows of London's Guildhall, commemorating the work of London Fire Brigade during the Blitz of 1940-1, when the building was seriously damaged. Such cases remind one that major restoration projects are an opportunity, not only to recreate past work and make it safe to hand on to future generations, but also an opportunity to add something precious and creative.
Should there be any doubt about what can be achieved in reconstruction, the example to look at is the Frauenkirche in Dresden, which was built in 1726-43. The fire-bombing of the city in 1945 reduced this magnificent Baroque temple to a few unrecognisable pieces of wall. In 1993, after Germany had been reunified, reconstruction finally began. It was completed in the mid-2000s, using as many of the original materials as possible. This was a local, national and international project, meticulous in its planning and execution. That is how another Church of Our Lady was given back to the people. It can be done again in Paris.
