On the Cusp

Or, “What’s a cwt, Uncle Andrew?”

I was visiting my mother last weekend and picked up a science book which I read as a teenager, but which originally belonged to my grandfather. It’s a brilliant discussion of materials science by Sir William Bragg, based on some Royal Institution lectures he did. I was thinking of passing it on to the next generation, but then I read the following sentence:

“The weight of air in the Royal Institution lecture theatre is about 15 cwt; the weight of argon is about 18 lbs”

I realised that this might be a bit of a puzzle for a current youngster, but I was intrigued to find out how far such dreadful ignorance extends. I therefore conducted a moderately scientific test, by asking a group of friends, relatives and colleagues the following: “Who can, without cheating (e.g. Google, scientific calculators etc.), tell me what percentage argon is by weight on this basis?” The victims were all bright boys and girls, but represented a wide spread of ages (19-65) and educational and ethnic backgrounds.

I knew the answer, but I had to think about it.

What surprised me was that I only got one other correct answer. From Ken, who is “about 60”. None of my other respondents had a clue, even those who are slightly older than myself.

So I appear to be pretty much the last of a breed who can work with a system of units based on 12, 14 and 16 as well as 10. Does this bode ill for our mental agility?

If you’re interested in the answer, I’ll post it as a comment, so you can have a go without cheating!

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One Response to On the Cusp

  1. Andrew says:

    OK, here’s the answer. Cwt stands for “hundredweight”, but as you might expect there are not 100 lbs in a cwt, but 112. You can either just remember this, or remember that there are eight stone in a cwt, or that there are 2240 lbs in a ton, and 20 cwt in a ton…

    Therefore the answer is 0.95%. I would accept a quick guess of 1%.

    I suppose the ideal prize would be a hundredweight of nutty slack. And no, Thomas, that’s not a sort of toffee :)

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