A letter of note from Isambard K. Brunel, civil engineer

On May 24, 1847, a bridge over the Dee River in Chester, England, collapsed. A passenger train plunged into the river; five people were killed and nine seriously injured.

The subsequent investigation blamed the bridge’s cast iron girders. Cast iron, like concrete but unlike wrought iron or steel, is strong in compression but weak in tension, and it is brittle, meaning that it breaks all at once, rather than deforming. The wrought iron trusses evidently were not enough to strengthen the girder.

In response to the disaster, a Royal Commission on the Application of Iron to Railway Structures was created in August of that year, “to inquire into the conditions to be observed by engineers in the application of iron in structures exposed to violent concussions and vibration”—that is, to set up standards and requirements, or as they were known in France at the time, règles de l’art.

In their investigation, the Commission solicited the opinion of one of the most eminent engineers of the age, Isambard Kingdom Brunel. But his response was, presumably, not what they expected.

Brunel begins his letter by saying that he is sorry they asked for his opinion, because of “my doubts of the advantage of such an enquiry, and my fears of its being, on the contrary, productive of much mischief, both to science and to the profession.” (Brunel’s son, writing his biography, says that he called them “The Commission for Stopping Further Improvements in Bridge Building.“) But since they did ask, he felt it necessary to state his full and honest views.

While he was happy to give his engineering opinion to the commission, he warned that

… the attempt to collect and re-issue as facts, with the stamp of authority, all that may be offered gratuitously to a Commission in the shape of evidence or opinions, to stamp with the same mark of value statements and facts, hasty opinions and well-considered and matured convictions, the good and the bad, the metal and the dross … this, I believe, always has rendered, and always will render, such collections of miscalled evidence injurious instead of adv