Thursday, March 15, 2012

Structures or why things don't fall down: Theory versus Pragmatism.

Extracts from: Structures or why things don't fall down by J.E. Gordon, published by Pelican Books 1978, reprinted Penguin books 1991. pgs 61 to 64.

Of the Scottish engineer, Thomas Telford (1757-1834), whose magnificent bridges we can still admire, it is related that:

He had a singular distaste for mathematic studies, and never even made himself acquainted with the elements of geometry; so remarkable indeed was this peculiarity that when we had occassion to recommend to him a young friend as a noephyte in his office, and founded our recommendation on his having distinguished himself in mathematics, he did not hesitate to say that he considered such requirements as rather disqualifying than fitting him for the situation.

Telford, however, really was a great man, and like Nelson, he tempered his confidence with an attractive humility. When the heavy chains for the Menai suspension bridge had been hoisted successfully in the presence of a large crowd, Telford was discovered, away from the cheering spectators, giving thanks on his knees.

Not all engineers were inwardly humble as Telford, and Anglo-Saxon attitudes at this time were often tinged, not only with intellectual idleness, but also with arrogance.


They felt that theoreticians were too often blinded by the elegance of their methods to the neglect of their assumptions, so that they produced the right answer to the wrong sum. In other words, they feared that the arrogance of mathematicians might be more dangerous than the arrogance of pragmatists, who, after all, were more likely to have been chastened by practical experience.


A deep, intuitive appreciation of the inherent cussedness of materials and structures is one of the most valuable accomplishments an engineer can have. No purely intellectual quality is really a substitute for this. Bridges designed upon the best 'modern' theories by Polytechniciens like Navier sometimes fell down. As far as I know, none of the hundreds of bridges and other engineering works which Telford built in the course of his long professional life ever gave serious trouble. Thus, during the period when French structural theory was outstanding, a great proportion of the railways and bridges on the Continent were being built by gritty and taciturn English and Scottish engineers who had little respect for the calculus.

All the same, after about 1850 even British and American engineers did begin to do calculations about the strength of important structures, such as large bridges.