"They handed me the Portland cement, and all the specification said was, 'All concrete shall consist of 1 of Portland cement to 6 of clean gravel, and shall be mixed and deposited in a workmanlike manner [which we consider means as the workmen like] to the entire satisfaction of the Company's engineer.'
"This was drawn up by a civil and mechanical engineer, which is a big-drum kind of title, and I should think covered corkscrews and manufacturing machinery, and everything else under the sun that can be handled at any time, including a 6-inch drain, the Forth Bridge, and the Channel Tunnel thrown in. It's too much, it seems to me, for one man to completely understand; and I once heard a celebrated engineer say that, with a few brilliant exceptions, such a man knew thoroughly neither civil nor mechanical engineering—life was too short. I don't presume to say anything, but his specifications of our kind of work might have been more exact; still they were sources of joy and comfort to us.
"Machine mixing was hardly known at the time I am particularly referring to, and the Portland cement was of all qualities, good, bad, and indifferent, and some as I really can't say had any quality in it at all, and was utterly unlike what you get now. It was then sometimes bought on the same principle as going to the first shop handy, and saying, 'Small bag of cement. How much?' There was no name on the bag, for no one wished to own he had made the cement, and it was indeed of illegitimate origin, and had no parents.
"The cement came, and we did pretty well as we liked, for the inspector knew nothing about it; in fact, we were all in the same boat. But what a lucky thing it is that there is such a thing as a margin of safety!"
"You mean the difference between the strain a thing has to bear in ordinary use and what will break it?"
"Yes, that is it. One day an engineer said to me, 'There is a large factor of safety in this case, which is fortunate.' I thought he was talking about a flour factor near the works that also sold fire-escapes and fire-extinguishers, so I said, 'He weighs nearly eighteen stone, and I should call him big rather than large, for he is like the prices at which he sells flour, and charges a penny a quartern too much; but he is greatly respected in the neighbourhood by those who don't know what fair prices are, for he is so oily and civil, as just suits a lot.' Between you and me, he swindled them, and beat us for 'extra' profit.
"The engineer looked as if he could not at first make out what I was talking about, and, as it turned out, I did not know what he was. He seemed to enjoy himself, and let me finish my sermon. He then explained to me what we call 'margins' of safety, and what they call 'factors' of safety are the same goods."
"You have learnt something now."
"I have, another name; no doubt their word is the right one, but they ought to consider the likes of us are not poets, or fed on stewed grammar, and should remember we were boss-gangers once, and have blossomed into sub-contractors.
"Let that pass. You should have seen the cement. It was lucky we never had to sift it as we do now, or we should never have got any through a forty-to-the-inch mesh. It was just like fine sand, and nearly the colour of it, too, instead of grey. I have had a fair experience with Portland cement now, for we had testing-rooms, machines and troughs, fresh and sea water, slabs, and a host of other detective apparatus at the last dock works I was on. However, the cement we had and I was just referring to, was pretty nearly all residue, and of course it did not stick the gravel together except in streaks that had good luck rather than anything else. And the gravel! Well, it is an elastic truth to call it gravel, for it was dirty; and I conscientiously feel I am close to thinking I am not speaking in accordance with the principles of strict veracity if I call it gravel.