Heirloom

How many of you are old enough to have learned how to use one of these at school? For once, I can gleefully say that I'm not. It's a slide rule, of course, and it's what people had before they invented pocket calculators.

It works on the same principle as log tables. I'm too young to have been taught those, too, though naturally I did learn about logarithms, so I do understand how they were used.

This was my father's, probably circa 1970, when he was getting some qualifications to make up for the fact that he'd left school at 15. My mother found it a while after he died, and being a young mathematics student I was fascinated by it, and started to use it. For most calculations it gives an accurate enough answer - generally 2 or 3 significant figures.

It's difficult to see a use for it in our computer age, and being plastic it's not very decorative. However, it is one of the few things I have that I really value - simple (it's just two pieces of plastic that slide), yet highly functional. I must admit, though, that the last time I used it was to draw a straight line...