I f you get the opportunity to attend one of Professor Bill Harvey’s lectures on masonry structures I suggest that you don’t let it slip by.

Bill’s lectures are both informative and entertaining, and often start with the following cautionary quote from Dr AR Dyke, who when addressing the Institution of Structural Engineers in 1976 made the following comment:

 “Engineering is the art of modelling materials we do not wholly understand, into shapes we cannot precisely analyse so as to withstand forces we cannot properly assess, in such a way that the public has no reason to suspect the extent of our ignorance”.


There has been debate about whether Dr Dyke was the originator of this assertion, but whether he was or wasn’t, I think it remains generally true. Nevertheless, I remain a little uncomfortable with his last line.

Raymond J Roark in his widely used book “Formulas for Stress and Strain”, first published in 1938, raised the same issue, but with considerably less drama:

“No calculated value of stress, strength, or deformation can be regarded as exact. The formulas used are based on certain assumptions as to properties of materials, regularity and form, and boundary conditions that are only approximately true, and they are derived by mathematical procedures that often involve further approximations. In general, therefore, great precision in numerical work is not justified. Each individual problem requires the exercise of judgement, and it is impossible to lay down rigid rules of procedure, …..”

 I have a fairly old edition of the book dating back to the late 1960’s, and in that edition the statement is made on page 58 under the heading of  “Remarks on the use of Formulas”. In my view it should have been made at the beginning of chapter 1, and restated at the start of virtually every chapter thereafter.

These two quotes came to mind recently when I read a thread in a web based technical group between two engineers enthusiastically debating the merits of one analytical software package against another. Their comments were based solely on ease of use, neither delved into the assumptions underpinning either of the packages.

In his book, The Lives of the Engineers” first published in the 1860’s Samuel Smiles commented that:

Not only were all the early engineers self taught in their profession, but they were brought up mostly in remote country places. ———- Strange indeed, that the men who built our bridges, docks, lighthouses, canals and railways should nearly all have been country-bred boys

He was referring mostly to the likes of Brindley, Smeaton, Rennie, Stevenson (George), and of course the prime example, Thomas Telford the first President of the Institution of Civil Engineers.

In the charter of the ICE civil engineering is described, in part, as:

The art of directing the great sources of power in nature for the use and convenience of man.”

 I have never been comfortable with this description, and in the course of my career have come to the conclusion that a bit more humility and respect is required when dealing with those forces. Here I think I am aligned with Dr. Dykes view of things. But perhaps those forces are more easily observed and understood in a country setting than in the hustle of a great metropolis, hence Samuel Smiles’ very valid observation.

Born the son of a shepherd in a remote area of the Scottish borders, Telford’s working life started at the age of 14 as a stonemason, and ended at the age of 77 when he held the office of the first President of the Institution of Civil Engineers, a position which he held for 14 years until his death in 1834.

I am not exactly sure when he wrote the following comments regarding the career development of young civil engineers, but I am fairly confident that it was late in his career when he was President of the ICE:

“Youths of respectability and competent education, who contemplate Civil Engineering as a profession, are seldom aware how far they ought to descend in order to found the basis of future elevation. 

 Not only are the natural senses of seeing and feeling requisite in the examination of materials, but also the practised eye, and the hand which has experience of the kind and qualities of stone, of lime, of iron, of timber, and even of earth, and

of the effects of human ingenuity in applying and combining all these substances – is necessary for arriving at mastery in the profession: for how can a man give judicious directions unless he possesses personal knowledge of the details requisite to effect his ultimate purpose in the best and cheapest manner?

 It has happened to me more than once, when taking opportunities of being useful to a young man of merit, that I have experienced opposition in taking him from his books and drawings, and placing a mallet,   chisel or trowel in his hand, till, rendered confident by the solid knowledge which experience only can bestow, he was qualified to insist on the due performance of workmanship, and to judge of merit in the lower as well as the higher departments of a profession in which no kind or degree of practical knowledge is superfluous.

 For this reason I ever congratulate myself upon the circumstances which compelled me to begin by working with my own hands, and thus to acquire early experience of the habits and feelings of workmen; it being equally important to the Civil Engineer, as to the Naval or Military Commanders, to have passed through all the grades of their profession.”

 Of course when Telford wrote these comments modern civil engineering was in its infancy, and compared to today the body of recorded knowledge and experience was not great, so arguably getting out there and experiencing construction first hand was more important in those days. Curious, therefore, that any aspiring young civil engineer would stand in front of the great man and say, “Sorry Mr. Telford, I don’t really feel like going to site today.”

So where does all this lead us?

I think that the comments of Raymond Roark and Dr. AR Dyke as no less true today than when they were first made.

Those of us who started our engineering careers with slide rules and log tables would certainly not want to dispose of the computers on our desks, but despite the speed and apparent precision the output is still an approximation.

A number of years back an old friend and colleague invited me to attend his inaugural lecture on his appointment to the chair of engineering at one of our long established universities. He touched on this point, explaining that in making our calculations, in most cases, we are seeking to gain sufficient confidence to construct, rather than seeking absolute answers.

In the majority of cases the assumptions and approximations made in our engineering calculations lead to safe and satisfactory results. But in some instances they may not, and this is when judgment based on experience comes to the fore, and the views of Thomas Telford, that no of level practical experience is too much in exercising engineering judgment, is just as relevant today as it was nearly 200 years ago.

In an industry such as steel bridge construction, which has been in decline for nearly three decades, the body of practical experience among its professionals inevitably becomes diluted.

Here Codorus through its network of seasoned and experienced engineers can help on the more complex issues that may arise, and hopefully before expenses for any of the parties involved start to escalate.


For assistance contact – geoff@codorus.co.uk.


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