When calculating needed to be understood
It’s my student-days British Thornton slide rule. Lying lost in a box in the attic. Okay, ChatGPT, do your stuff and tell me all about it.
It’s a P271, a final-generation model from 1975.
I already knew that.
It was supplied in either a leatherette case or a vinyl snap case.
Mine is vinyl.
By the mid-1970s, Japanese calculators were becoming cheaper, faster, and more readily available. The P271 was high-end: about £18 in 1975, when the average weekly wage was £70.
I have no recollection of buying mine, or how much it cost. But £18 would have been over fifty beers — a few good nights out. I’ve no memory of where I got the money from.
Thornton was founded in Manchester in 1916 and became the British slide-rule maker. Known for its phenolic laminate bodies, excellent engraving, and durable cursors, its rules were exported throughout the Commonwealth.
Good. I like Manchester. The first place I lived after university.
Phenolic laminate is made by impregnating layers of paper or cotton with phenol-formaldehyde resin, then compressing and curing them under heat and pressure.
Like a dead body is preserved?
I have questions.
Don’t burn it and sniff the fumes. It’s very dangerous.
Well, that’s spoiled my plans — but good to know.
I spent four years studying mathematics at the University of Glasgow and can hardly remember ever having to calculate numbers using fingers, pen and paper, a slide rule, or a calculator. Those things were for engineers.
Looking at it now, I can see my youthful grubby finger marks, so I must have used it sometimes.
For drawing straight lines, I suspect.
@ Copyright 2026 Steve Gillies. All right reserved.
Steve Gillies 
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